Imperial College London

ProfessorTimothySumner

Faculty of Natural SciencesDepartment of Physics

Professor of Experimental Astrophysics
 
 
 
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Contact

 

+44 (0)20 7594 7552t.sumner

 
 
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Location

 

1108Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

416 results found

Touboul P, Métris G, Rodrigues M, André Y, Baghi Q, Bergé J, Boulanger D, Bremer S, Chhun R, Christophe B, Cipolla V, Damour T, Danto P, Dittus H, Fayet P, Foulon B, Guidotti P-Y, Hardy E, Huynh P-A, Lämmerzahl C, Lebat V, Liorzou F, List M, Panet I, Pires S, Pouilloux B, Prieur P, Reynaud S, Rievers B, Robert A, Selig H, Serron L, Sumner T, Visser Pet al., 2019, Space test of the equivalence principle: first results of the MICROSCOPE mission, Classical and Quantum Gravity, Vol: 36, Pages: 225006-225006, ISSN: 0264-9381

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Hartig M-S, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson D, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe J, Trenkel C, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, Novel methods to measure the gravitational constant in space, PHYSICAL REVIEW D, Vol: 100, ISSN: 2470-0010

Journal article

Thorpe J, Slutsky J, Baker JG, Littenberg TB, Hourihane S, Pagane N, Pokorny P, Janches D, Armano M, Audley H, Auger G, Baird J, Bassan M, Binetruy P, Born M, Bortoluzzi D, Brandt N, Caleno M, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, De Rosa R, Di Fiore L, Diepholz I, Dixon G, Dolesi R, Dunbar N, Ferraioli L, Ferroni V, Fitzsimons ED, Flatscher R, Freschi M, Marirrodriga CG, Gerndt R, Gesa L, Gibert F, Giardini D, Giusteri R, Grado A, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Johlander B, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Madden S, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Prat P, Ragnit U, Ramos-Castro J, Reiche J, Robertson D, Rozemeijer H, Rivas F, Russano G, Sarra P, Schleicher A, Shaul D, Sopuerta CF, Stanga R, Sumner T, Texier D, Trenkel C, Troebs M, Vetrugno D, Vitale S, Wanner G, Ward H, Wass P, Wealthy D, Weber WJ, Wissel L, Wittchen A, Zambotti A, Zanoni C, Ziegler T, Zweifel P, Barela P, Cutler C, Demmons N, Dunn C, Girard M, Hsu O, Javidnia S, Li I, Maghami P, Marrese-Reading C, Mehta J, O'Donnell J, Romero-Wolf A, Ziemer Jet al., 2019, Micrometeoroid events in LISA pathfinder, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 883, Pages: 1-15, ISSN: 0004-637X

The zodiacal dust complex, a population of dust and small particles that pervades the solar system, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. We present a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory. Pathfinder employed a technique known as drag-free control that achieved rejection of external disturbances, including particle impacts, using a micropropulsion system. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hr of Pathfinder data. We report a total of 54 candidates with transferred momenta ranging from 0.2 to 230 μNs. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system, including those resulting from Jupiter-family comets (JFCs), Oort Cloud comets, Halley-type comets, and asteroids. We find that our measured population is consistent with a population dominated by JFCs, with some evidence for a smaller contribution from Halley-type comets, in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, Silva MDD, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Hartig M-S, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, LISA pathfinder performance confirmed in an open-loop configuration: results from the free-fall actuation mode, Physical Review Letters, Vol: 123, Pages: 111101-1-111101-7, ISSN: 0031-9007

We report on the results of the LISA Pathfinder (LPF) free-fall mode experiment, in which the control force needed to compensate the quasistatic differential force acting on two test masses is applied intermittently as a series of “impulse” forces lasting a few seconds and separated by roughly 350 s periods of true free fall. This represents an alternative to the normal LPF mode of operation in which this balancing force is applied continuously, with the advantage that the acceleration noise during free fall is measured in the absence of the actuation force, thus eliminating associated noise and force calibration errors. The differential acceleration noise measurement presented here with the free-fall mode agrees with noise measured with the continuous actuation scheme, representing an important and independent confirmation of the LPF result. An additional measurement with larger actuation forces also shows that the technique can be used to eliminate actuation noise when this is a dominant factor.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Balajthy J, Baxter A, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Boxer B, Bras P, Burdin S, Byram D, Carmona-Benitez MC, Chan C, Cutter JE, de Viveiros L, Druszkiewicz E, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Gwilliam C, Hall CR, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Jahangir O, Ji W, Kamdin K, Kazkaz K, Khaitan D, Korolkova E, Kravitz S, Kudryavtsev VA, Leason E, Lenardo BG, Lesko KT, Liao J, Lin J, Lindote A, Lopes M, Manalaysay A, Mannino RL, Marangou N, Marzioni MF, McKinsey DN, Mei D-M, Moongweluwan M, Morad JA, Murphy ASJ, Naylor A, Nehrkorn C, Nelson HN, Neves F, Nilima A, Oliver-Mallory KC, Palladino KJ, Pease EK, Riffard Q, Rischbieter GRC, Rhyne C, Rossiter P, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor R, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Utku U, Uvarov S, Vacheret A, Velan V, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Woodward D, Xu J, Zhang Cet al., 2019, Improved measurements of the beta-decay response of liquid xenon with the LUX detector, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, ISSN: 1550-2368

We report results from an extensive set of measurements of the β-decay response in liquid xenon. These measurements are derived from high-statistics calibration data from injected sources of both 3H and 14C in the LUX detector. The mean light-to-charge ratio is reported for 13 electric field values ranging from 43 to 491  V/cm, and for energies ranging from 1.5 to 145 keV.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Mansanet C, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Meshksar N, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Sanjuan J, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Trenkel C, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Wealthy D, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, Temperature stability in the sub-milliHertz band with LISA Pathfinder, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 486, Pages: 3368-3379, ISSN: 0035-8711

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, LISA Pathfinder micronewton cold gas thrusters: In-flight characterization, PHYSICAL REVIEW D, Vol: 99, ISSN: 2470-0010

Journal article

Wass PJ, Hollington D, Sumner TJ, Yang F, Pfeil Met al., 2019, Effective decrease of photoelectric emission threshold from gold plated surfaces, Review of Scientific Instruments, Vol: 90, ISSN: 0034-6748

Many applications require charge neutralization of isolated test bodies, and this has been successfully done using photoelectric emission from surfaces which are electrically benign (gold) or superconducting (niobium). Gold surfaces nominally have a high work function (∼5.1 eV) which should require deep UV photons for photoemission. In practice, it has been found that it can be achieved with somewhat lower energy photons with indicative work functions of (4.1–4.3 eV). A detailed working understanding of the process is lacking, and this work reports on a study of the photoelectric emission properties of 4.6 × 4.6 cm2 gold plated surfaces, representative of those used in typical satellite applications with a film thickness of 800 nm, and measured surface roughnesses between 7 and 340 nm. Various UV sources with photon energies from 4.8 to 6.2 eV and power outputs from 1 nW to 1000 nW illuminated ∼0.3 cm2 of the central surface region at angles of incidence from 0° to 60°. Final extrinsic quantum yields in the range 10 ppm–44 ppm were reliably obtained during 8 campaigns, covering a period of ∼3 years but with intermediate long-term variations lasting several weeks and, in some cases, bake-out procedures at up to 200 °C. Experimental results were obtained in a vacuum system with a baseline pressure of ∼10−7 mbar at room temperature. A working model, designed to allow accurate simulation of any experimental configuration, is proposed.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, LISA Pathfinder platform stability and drag-free performance, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 99, ISSN: 1550-2368

The science operations of the LISA Pathfinder mission have demonstrated the feasibility of sub-femto-g free fall of macroscopic test masses necessary to build a gravitational wave observatory in space such as LISA. While the main focus of interest, i.e., the optical axis or the x-axis, has been extensively studied, it is also of great importance to evaluate the stability of the spacecraft with respect to all the other degrees of freedom (d.o.f.). The current paper is dedicated to such a study: the exhaustive and quantitative evaluation of the imperfections and dynamical effects that impact the stability with respect to its local geodesic. A model of the complete closed-loop system provides a comprehensive understanding of each component of the in-loop coordinates spectral density. As will be presented, this model gives very good agreement with LISA Pathfinder flight data. It allows one to identify the noise source at the origin and the physical phenomena underlying the couplings. From this, the stability performance of the spacecraft with respect to its geodesic is extracted as a function of frequency. Close to 1 mHz, the stability of the spacecraft on the XSC, YSC and ZSC d.o.f. is shown to be of the order of 5.0×10−15  m s−2 Hz−1/2 for X, 6.0×10−14  m s−2 Hz−1/2 for Y, and 4.0×10−14  m s−2 Hz−1/2 for Z. For the angular d.o.f., the values are of the order of 3×10−12  rad s−2  Hz−1/2 for ΘSC, 5×10−13  rad s−2  Hz−1/2 for HSC, and 3×10−13  rad s−2  Hz−1/2 for ΦSC. Below 1 mHz, however, the stability performances are worsened significantly by the effect of the star tracker noise on the closed-loop system. It is worth noting that LI

Journal article

Armano M, Audley H, Baird J, Benella S, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Fabi M, Ferraioli L, Ferroni V, Finetti N, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Kudela K, Laurenza M, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson D, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Telloni D, Texier D, Thorpe J, Vetrugno D, Villani M, Vitale S, Wanner G, Ward H, Wass P, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2019, Forbush Decreases and < 2 Day GCR Flux Non-recurrent Variations Studied with LISA Pathfinder, Astrophysical Journal, Vol: 874, ISSN: 0004-637X

Non-recurrent short-term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n−1 were observed between 2016 February 18 and 2017 July 3 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 106 km from Earth. The energy dependence of three Forbush decreases is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n−1 shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence are also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration <2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing causes the majority of the depressions.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Boxer B, Bras P, Burdin S, Byram D, Carmona-Benitez MC, Chan C, Cutter JE, Davison TJR, Druszkiewicz E, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Gwilliam C, Hall CR, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Jahangir O, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Korolkova E, Kravitz S, Kudryavtsev VA, Lenardo BG, Lesko KT, Liao J, Lin J, Lindote A, Lopes M, Manalaysay A, Mannino RL, Marangou N, Marzioni MF, McKinsey DN, Mei D-M, Moongweluwan M, Morad JA, Murphy ASJ, Naylor A, Nehrkorn C, Nelson HN, Neves F, Oliver-Mallory KC, Palladino KJ, Pease EK, Riffard Q, Rischbieter GRC, Rhyne C, Rossiter P, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Utku U, Uvarov S, Velan V, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Woodward D, Xu J, Yazdani K, Zhang Cet al., 2019, Results of a Search for Sub-GeV Dark Matter Using 2013 LUX Data, PHYSICAL REVIEW LETTERS, Vol: 122, ISSN: 0031-9007

Journal article

Tomás A, Araújo HM, Bailey AJ, Bayer A, Chen E, López Paredes B, Sumner TJet al., 2018, Study and mitigation of spurious electron emission from cathodic wires in noble liquid time projection chambers, Astroparticle Physics, Vol: 103, Pages: 49-61, ISSN: 0927-6505

Noble liquid radiation detectors have long been afflicted by spurious electron emission from their cathodic electrodes. This phenomenon must be understood and mitigated in the next generation of liquid xenon (LXe) experiments searching for WIMP dark matter or neutrinoless double beta decay, and in the large liquid argon (LAr) detectors for the long-baseline neutrino programmes. We present a systematic study of this spurious emission involving a series of slow voltage-ramping tests on fine metal wires immersed in a two-phase xenon time projection chamber with single electron sensitivity. Emission currents as low as 10−18A can thus be detected by electron counting, a vast improvement over previous dedicated measurements. Emission episodes were recorded at surface fields as low as ∼ 10 kV/cm in some wires and observed to have complex emission patterns, with average rates of 10–200 counts per second (c/s) and outbreaks as high as ∼ 106c/s. A fainter, less variable type of emission was also present in all untreated samples. There is evidence of a partial conditioning effect, with subsequent tests yielding on average fewer emitters occurring at different fields for the same wire. We find no evidence for an intrinsic threshold particular to the metal-LXe interface which might have limited previous experiments up to fields of at least 160 kV/cm. The general phenomenology is not consistent with enhanced field emission from microscopic filaments, but it appears instead to be related to the quality of the wire surface in terms of corrosion and the nature of its oxide layer. This study concludes that some surface treatments, in particular nitric acid cleaning applied to stainless steel wires, can bring about at least order-of-magnitude improvements in overall electron emission rates, and this should help the next generation of detectors achieve the required electrostatic performance.

Journal article

Anderson G, Anderson J, Anderson M, Aveni G, Bame D, Barela P, Blackman K, Carmain A, Chen L, Cherng M, Clark S, Connally M, Connolly W, Conroy D, Cooper M, Cutler C, D'Agostino J, Demmons N, Dorantes E, Dunn C, Duran M, Ehrbar E, Evans J, Fernandez J, Franklin G, Girard M, Gorelik J, Hruby V, Hsu O, Jackson D, Javidnia S, Kern D, Knopp M, Kolasinski R, Kuo C, Le T, Li I, Liepack O, Littlefield A, Maghami P, Malik S, Markley L, Martin R, Marrese-Reading C, Mehta J, Mennela J, Miller D, Nguyen D, O'Donnell J, Parikh R, Plett G, Ramsey T, Randolph T, Rhodes S, Romero-Wolf A, Roy T, Ruiz A, Shaw H, Slutsky J, Spence D, Stocky J, Tallon J, Thorpe I, Tolman W, Umfress H, Valencia R, Valerio C, Warner W, Wellman J, Willis P, Ziemer J, Zwahlen J, Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesai L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jenntich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNatnara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson D, Rivas F, Russano G, Sopuerta CF, Sumner T, Texier D, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2018, Experimental results from the ST7 mission on LISA Pathfinder, Physical Review D, Vol: 98, ISSN: 2470-0010

The Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload that operated from January 2016 through July 2017 on the European Space Agency’s (ESA) LISA Pathfinder spacecraft. The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observatory targeting the source-rich millihertz band. The two primary components of ST7-DRS are a micropropulsion system based on colloidal micro-Newton thrusters (CMNTs) and a control system that simultaneously controls the attitude and position of the spacecraft and the two free-flying test masses (TMs). This paper presents our main experimental results and summarizes the overall performance of the CMNTs and control laws. We find the CMNT performance to be consistent with preflight predictions, with a measured system thrust noise on the order of 100  nN/√Hz in the 1  mHz≤f≤30  mHz band. The control system maintained the TM-spacecraft separation with an RMS error of less than 2 nm and a noise spectral density of less than 3  nm/√Hz in the same band. Thruster calibration measurements yield thrust values consistent with the performance model and ground-based thrust-stand measurements, to within a few percent. We also report a differential acceleration noise between the two test masses with a spectral density of roughly 3  fm/s2/√Hz in the 1  mHz≤f≤30  mHz band, slightly less than twice as large as the best performance reported with the baseline LISA Pathfinder configuration and below the current requirements for the Laser Interferometer Space Antenna mission.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Boxer B, Bras P, Burdin S, Byram D, Carmona-Benitez MC, Chan C, Cutter JE, Davison TJR, Druszkiewicz E, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Grace E, Gwilliam C, Hall CR, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Korolkova EV, Kravitz S, Kudryavtsev VA, Lenardo BG, Lesko KT, Liao J, Lin J, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marangou N, Marzioni MF, McKinsey DN, Mei D-M, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, Oliver-Mallory KC, Palladino KJ, Pease EK, Rischbieter G, Rhyne C, Rossiter P, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Utku U, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Woodward D, Xu J, Yazdani K, Zhang Cet al., 2018, LUX trigger efficiency, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 908, Pages: 401-410, ISSN: 0168-9002

The Large Underground Xenon experiment (LUX) searches for dark matter using a dual-phase xenon detector. LUX uses a custom-developed trigger system for event selection. In this paper, the trigger efficiency, which is defined as the probability that an event of interest is selected for offline analysis, is studied using raw data obtained from both electron recoil (ER) and nuclear recoil (NR) calibrations. The measured efficiency exceeds 98% at a pulse area of 90 detected photons, which is well below the WIMP analysis threshold on the S2 pulse area. The efficiency also exceeds 98% at recoil energies of 0.2 keV and above for ER, and 1.3 keV and above for NR. The measured trigger efficiency varies between 99% and 100% over the fiducial volume of the detector.

Journal article

Paredes BL, Araujo HM, Froborg E, Marangou N, Olcina I, Sumner TJ, Taylor R, Tomas A, Vacheret Aet al., 2018, Response of photomultiplier tubes to xenon scintillation light, Astroparticle Physics, Vol: 102, Pages: 56-66, ISSN: 0927-6505

We present the precision calibration of 35 Hamamatsu R11410-22 photomultiplier tubes (PMTs) with xenon scintillation light centred near 175 nm. This particular PMT variant was developed specifically for the LUX-ZEPLIN (LZ) dark matter experiment. A room-temperature xenon scintillation cell coupled to a vacuum cryostat was used to study the full-face PMT response at both room and low temperature ( ∼ −100 °C), in particular to determine the quantum efficiency (QE) and double photoelectron emission (DPE) probability in LZ operating conditions. For our sample with an average QE of (32.4  ±  2.9)% at room temperature, we find a relative improvement of (17.9  ±  5.2)% upon cooling (where uncertainty values refer to the sample standard deviation). The mean DPE probability in response to single vacuum ultraviolet (VUV) photons is (22.6  ±  2.0)% at low temperature; the DPE increase relative to room temperature, measured here for the first time, was (12.2  ±  3.9)%. Evidence of a small triple photoelectron emission probability ( ∼ 0.6%) has also been observed. Useful correlations are established between these parameters and the QE as measured by the manufacturer. The single VUV photon response is also measured for one ETEL D730/9829QB, a PMT with a more standard bialkali photocathode used in the ZEPLIN-III experiment, for which we obtained a cold DPE fraction of (9.1  ±  0.1)%. Hence, we confirm that this effect is not restricted to the low-temperature bialkali photocathode technology employed by Hamamatsu. This highlights the importance of considering this phenomenon in the interpretation of data from liquid xenon scintillation and electroluminescence detectors, and from many other optical measurements in this wavelength region.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Boxer B, Bras P, Burdin S, Byram D, Carmona-Benitez MC, Chan C, Cutter JE, Davison TJR, Druszkiewicz E, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Gwilliam C, Hall CR, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Korolkova EV, Kravitz S, Kudryavtsev VA, Lenardo BG, Lesko KT, Liao J, Lin J, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marangou N, Marzioni MF, McKinsey DN, Mei D-M, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, Oliver-Mallory KC, Palladino KJ, Pease EK, Rischbieter GRC, Rhyne C, Rossiter P, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Utku U, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Woodward D, Xu J, Yazdani K, Zhang Cet al., 2018, Search for annual and diurnal rate modulations in the LUX experiment, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 98, ISSN: 1550-2368

Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth’s motion in the halo. Observation of such features can provide generic evidence for detection of dark matter interactions. This paper reports a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of 2.3±0.2 cpd/keVee/tonne, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to 26 keVee. Between 2 and 6 keVee, this analysis demonstrates the most sensitive annual modulation search up to date, with 9.2σ tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above 0.2 cpd/keVee/tonne amplitude between 2 and 6 keVee.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Giardini D, Gibert F, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Liu L, Lloro I, Lobo JA, Lopez-Zaragoza JP, Maarschalkerweerd R, Mailland F, Mance D, Martin V, Martin-Polo L, Martin-Porqueras F, Martino J, Mateos I, McNamara PW, Mendes J, Mendes L, Meshskar N, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pfeil M, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson D, Rivas F, Russano G, Santoruvo G, Sarra P, Shaul D, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe J, Trenkel C, Vetrugno D, Vitale S, Wanner G, Ward H, Waschke S, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2018, Precision charge control for isolated free-falling test masses: LISA pathfinder results, Physical Review D, Vol: 98, ISSN: 2470-0010

The LISA Pathfinder charge management device was responsible for neutralizing the cosmic-ray-induced electric charge that inevitably accumulated on the free-falling test masses at the heart of the experiment. We present measurements made on ground and in flight that quantify the performance of this contactless discharge system which was based on photoemission under UV illumination. In addition, a two-part simulation is described that was developed alongside the hardware. Modeling of the absorbed UV light within the Pathfinder sensor was carried out with the Geant4 software toolkit and a separate Matlab charge transfer model calculated the net photocurrent between the test masses and surrounding housing in the presence of AC and DC electric fields. We confront the results of these models with observations and draw conclusions for the design of discharge systems for future experiments like LISA that will also employ free-falling test masses.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson D, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe J, Vetrugno D, Vitale S, Wanner G, Ward H, Wass P, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2018, Calibrating the system dynamics of LISA Pathfinder, Physical Review D, Vol: 97, ISSN: 2470-0010

LISA Pathfinder (LPF) was a European Space Agency mission with the aim to test key technologies for future space-borne gravitational-wave observatories like LISA. The main scientific goal of LPF was to demonstrate measurements of differential acceleration between free-falling test masses at the sub-femto-g level, and to understand the residual acceleration in terms of a physical model of stray forces, and displacement readout noise. A key step toward reaching the LPF goals was the correct calibration of the dynamics of LPF, which was a three-body system composed by two test-masses enclosed in a single spacecraft, and subject to control laws for system stability. In this work, we report on the calibration procedures adopted to calculate the residual differential stray force per unit mass acting on the two test-masses in their nominal positions. The physical parameters of the adopted dynamical model are presented, together with their role on LPF performance. The analysis and results of these experiments show that the dynamics of the system was accurately modeled and the dynamical parameters were stationary throughout the mission. Finally, the impact and importance of calibrating system dynamics for future space-based gravitational wave observatories is discussed.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Druszkiewicz E, Edwards BN, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Hall CR, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Lenardo BG, Lesko KT, Liao J, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Utku U, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2018, Liquid xenon scintillation measurements and pulse shape discrimination in the LUX dark matter detector, PHYSICAL REVIEW D, Vol: 97, ISSN: 2470-0010

Weakly interacting massive particles (WIMPs) are a leading candidate for dark matter and are expected to produce nuclear recoil (NR) events within liquid xenon time-projection chambers. We present a measurement of the scintillation timing characteristics of liquid xenon in the LUX dark matter detector and develop a pulse shape discriminant to be used for particle identification. To accurately measure the timing characteristics, we develop a template-fitting method to reconstruct the detection times of photons. Analyzing calibration data collected during the 2013–2016 LUX WIMP search, we provide a new measurement of the singlet-to-triplet scintillation ratio for electron recoils (ER) below 46 keV, and we make, to our knowledge, a first-ever measurement of the NR singlet-to-triplet ratio at recoil energies below 74 keV. We exploit the difference of the photon time spectra for NR and ER events by using a prompt fraction discrimination parameter, which is optimized using calibration data to have the least number of ER events that occur in a 50% NR acceptance region. We then demonstrate how this discriminant can be used in conjunction with the charge-to-light discrimination to possibly improve the signal-to-noise ratio for nuclear recoils.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Cahn SB, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Dobson JEY, Druszkiewicz E, Edwards BN, Faham CH, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Gehman VM, Genovesi J, Ghag C, Gilchriese GD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lee C, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Reichhart L, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2018, Calibration, event reconstruction, data analysis, and limit calculation for the LUX dark matter experiment, PHYSICAL REVIEW D, Vol: 97, ISSN: 2470-0010

The LUX experiment has performed searches for dark-matter particles scattering elastically on xenon nuclei, leading to stringent upper limits on the nuclear scattering cross sections for dark matter. Here, for results derived from 1.4×104  kg days of target exposure in 2013, details of the calibration, event-reconstruction, modeling, and statistical tests that underlie the results are presented. Detector performance is characterized, including measured efficiencies, stability of response, position resolution, and discrimination between electron- and nuclear-recoil populations. Models are developed for the drift field, optical properties, background populations, the electron- and nuclear-recoil responses, and the absolute rate of low-energy background events. Innovations in the analysis include in situ measurement of the photomultipliers’ response to xenon scintillation photons, verification of fiducial mass with a low-energy internal calibration source, and new empirical models for low-energy signal yield based on large-sample, in situ calibrations.

Journal article

Armano M, Audley H, Baird J, Bassan M, Benella S, Binetruy P, Born M, Bortoluzzi D, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, Silva MDD, Diepholz I, Dixon G, Dolesi R, Fabi M, Ferraioli L, Ferroni V, Finetti N, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Laurenza M, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Sabbatini F, Slutsky J, Sopuerta CF, Sumner T, Telloni D, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass P, Weber WJ, Wissel L, Wittchen A, Zambotti A, Zenoni C, Zweifel Pet al., 2018, Characteristics and energy dependence of recurrent galactic cosmic-ray Flux depressions and of a Forbush decrease with LISA Pathfinder, Astrophysical Journal, Vol: 854, ISSN: 0004-637X

Galactic cosmic-ray (GCR) energy spectra observed in the inner heliosphere are modulated by the solar activity, the solar polarity and structures of solar and interplanetary origin. A high counting rate particle detector (PD) aboard LISA Pathfinder, meant for subsystems diagnostics, was devoted to the measurement of GCR and solar energetic particle integral fluxes above 70 MeV n−1 up to 6500 counts s−1. PD data were gathered with a sampling time of 15 s. Characteristics and energy dependence of GCR flux recurrent depressions and of a Forbush decrease dated 2016 August 2 are reported here. The capability of interplanetary missions, carrying PDs for instrument performance purposes, in monitoring the passage of interplanetary coronal mass ejections is also discussed.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise AM, Danzmann K, de Deus Silva M, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspé H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, López-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshksar N, Martín V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass PJ, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2018, Beyond the Required LISA Free-Fall Performance: New LISA Pathfinder Results down to 20  μHz., Physical Review Letters, Vol: 120, ISSN: 0031-9007

In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20  μHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05)  fm s^{-2}/sqrt[Hz] above 2 mHz and (6±1)×10  fm s^{-2}/sqrt[Hz] at 20  μHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Cahn SB, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Druszkiewicz E, Edwards BN, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2018, Position reconstruction in LUX, Journal of Instrumentation, Vol: 13, ISSN: 1748-0221

The (x, y) position reconstruction method used in the analysis of the complete exposure of the Large Underground Xenon (LUX) experiment is presented. The algorithm is based on a statistical test that makes use of an iterative method to recover the photomultiplier tube (PMT) light response directly from the calibration data. The light response functions make use of a two dimensional functional form to account for the photons reflected on the inner walls of the detector. To increase the resolution for small pulses, a photon counting technique was employed to describe the response of the PMTs. The reconstruction was assessed with calibration data including ⁸³mKr (releasing a total energy of 41.5 keV) and ³H (β− with Q = 18.6 keV) decays, and a deuterium-deuterium (D-D) neutron beam (2.45 MeV) . Within the detector's fiducial volume, the reconstruction has achieved an (x, y) position uncertainty of σ = 0.82 cm and σ = 0.17 cm for events of only 200 and 4,000 detected electroluminescence photons respectively. Such signals are associated with electron recoils of energies ~0.25 keV and ~10 keV, respectively. The reconstructed position of the smallest events with a single electron emitted from the liquid surface (22 detected photons) has a horizontal (x, y) uncertainty of 2.13 cm.

Journal article

Armano M, Audley H, Baird J, Binetruy P, Born M, Bortoluzzi D, Castelli E, Cavalleri A, Cesarini A, Cruise M, Danzmann K, Silva MDD, Diepholz I, Dixon G, Dolesi R, Ferraioli L, Ferroni V, Finetti N, Fitzsimons ED, Freschi M, Gesa L, Gibert F, Giardini D, Giusteri R, Grimani C, Grzymisch J, Harrison I, Heinzel G, Hewitson M, Hollington D, Hoyland D, Hueller M, Inchauspe H, Jennrich O, Jetzer P, Karnesis N, Kaune B, Korsakova N, Killow CJ, Lobo JA, Lloro I, Liu L, Lopez-Zaragoza JP, Maarschalkerweerd R, Mance D, Meshskar N, Martin V, Martin-Polo L, Martino J, Martin-Porqueras F, Mateos I, McNamara PW, Mendes J, Mendes L, Nofrarias M, Paczkowski S, Perreur-Lloyd M, Petiteau A, Pivato P, Plagnol E, Ramos-Castro J, Reiche J, Robertson DI, Rivas F, Russano G, Slutsky J, Sopuerta CF, Sumner T, Texier D, Thorpe JI, Vetrugno D, Vitale S, Wanner G, Ward H, Wass P, Weber WJ, Wissel L, Wittchen A, Zweifel Pet al., 2018, Measuring the Galactic Cosmic Ray Flux with the LISA Pathfinder Radiation Monitor, Astroparticle Physics, Vol: 98, Pages: 28-37, ISSN: 0927-6505

Test mass charging caused by cosmic rays will be a significant source ofacceleration noise for space-based gravitational wave detectors like LISA.Operating between December 2015 and July 2017, the technology demonstrationmission LISA Pathfinder included a bespoke monitor to help characterise therelationship between test mass charging and the local radiation environment.The radiation monitor made in situ measurements of the cosmic ray flux whilealso providing information about its energy spectrum. We describe the monitorand present measurements which show a gradual 40% increase in count ratecoinciding with the declining phase of the solar cycle. Modulations of up to10% were also observed with periods of 13 and 26 days that are associated withco-rotating interaction regions and heliospheric current sheet crossings. Thesevariations in the flux above the monitor detection threshold (approximately 70MeV) are shown to be coherent with measurements made by the IREM monitoron-board the Earth orbiting INTEGRAL spacecraft. Finally we use the measureddeposited energy spectra, in combination with a GEANT4 model, to estimate thegalactic cosmic ray differential energy spectrum over the course of themission.

Journal article

Baird JT, Hollington D, Sumner TJ, Wass PJet al., 2018, A fundamental test of gravity with LISA pathfinder, Pages: 3203-3209

Copyright © 2018 by the Editors.All rights reserved. This work builds on a private communication detailing the potential for a LISA Pathfinder (LPF) test of the inverse square law. Various sources are explored as tests of this law using basic calculations, and plotted with the potential contribution from LPF based on a measurement of the acceleration gradient through the Sun-Earth gravitational saddle point. It is found that an intermediate acceleration range could be filled by this measurement, but would not reach the lower accelerations that other systems have reached.

Conference paper

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balaithy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Cahn SB, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Druszkiewicz E, Edwards BN, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghang C, Gilchriese MGD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkom C, Nelson HN, Neves F, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2017, Ultralow energy calibration of LUX detector using Xe-127 electron capture, PHYSICAL REVIEW D, Vol: 96, ISSN: 2470-0010

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Cahn SB, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Druszkiewicz E, Edwards BN, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2017, 83mKr calibration of the 2013 LUX dark matter search, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 96, ISSN: 1550-2368

LUX was the first dark matter experiment to use a 83mKr calibration source. In this paper, we describe the source preparation and injection. We also present several 83mKr calibration applications in the context of the 2013 LUX exposure, including the measurement of temporal and spatial variation in scintillation and charge signal amplitudes, and several methods to understand the electric field within the time projection chamber.

Journal article

Touboul P, Metris G, Rodrigues M, Andre Y, Baghi Q, Berge J, Boulanger D, Bremer S, Carle P, Chhun R, Christophe B, Cipolla V, Damour T, Danto P, Dittus H, Fayet P, Foulon B, Gageant C, Guidotti P-Y, Hagedorn D, Hardy E, Phuong-Anh H, Inchauspe H, Kayser P, Lala S, Laemmerzahl C, Lebat V, Leseur P, Liorzou F, List M, Loeffler F, Panet I, Pouilloux B, Prieur P, Rebray A, Reynaud S, Rievers B, Robert A, Selig H, Serron L, Sumner T, Tanguy N, Visser Pet al., 2017, MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle, Physical Review Letters, Vol: 119, ISSN: 0031-9007

According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10−15 precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ(Ti,Pt)=[−1±9(stat)±9(syst)]×10−15 (1σ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations.

Journal article

Akerib DS, Alsum S, Araujo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bras P, Byram D, Cahn SB, Carmona-Benitez MC, Chan C, Currie A, Cutter JE, Davison TJR, Dobi A, Druszkiewicz E, Edwards BN, Fallon SR, Fan A, Fiorucci S, Gaitskell RJ, Genovesi J, Ghag C, Gilchriese MGD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei D-M, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Rhyne C, Shaw S, Shutt TA, Silva C, Solmaz M, Solovov VN, Sorensen P, Sumner TJ, Szydagis M, Taylor DJ, Taylor WC, Tennyson BP, Terman PA, Tiedt DR, To WH, Tripathi M, Tvrznikova L, Uvarov S, Velan V, Verbus JR, Webb RC, White JT, Whitis TJ, Witherell MS, Wolfs FLH, Xu J, Yazdani K, Young SK, Zhang Cet al., 2017, 3D modeling of electric fields in the LUX detector, Journal of Instrumentation, Vol: 12, ISSN: 1748-0221

This work details the development of a three-dimensional (3D) electric field model for the LUX detector. The detector took data to search for weakly interacting massive particles (WIMPs) during two periods. After the first period completed, a time-varying non-uniform negative charge developed in the polytetrafluoroethylene (PTFE) panels that define the radial boundary of the detector's active volume. This caused electric field variations in the detector in time, depth and azimuth, generating an electrostatic radially-inward force on electrons on their way upward to the liquid surface. To map this behavior, 3D electric field maps of the detector's active volume were generated on a monthly basis. This was done by fitting a model built in COMSOL Multiphysics to the uniformly distributed calibration data that were collected on a regular basis. The modeled average PTFE charge density increased over the course of the exposure from -3.6 to −5.5 μC/m2. From our studies, we deduce that the electric field magnitude varied locally while the mean value of the field of ~200 V/cm remained constant throughout the exposure. As a result of this work the varying electric fields and their impact on event reconstruction and discrimination were successfully modeled.

Journal article

Akerib DS, Araújo HM, Bai X, Bailey AJ, Balajthy J, Beltrame P, Bernard EP, Bernstein A, Biesiadzinski TP, Boulton EM, Bramante R, Cahn SB, Carmona-Benitez MC, Chan C, Chiller AA, Chiller C, Coffey T, Currie A, Cutter JE, Davison TJR, Dobi A, Dobson JEY, Druszkiewicz E, Edwards BN, Faham CH, Fiorucci S, Gaitskell RJ, Gehman VM, Ghag C, Gibson KR, Gilchriese MGD, Hall CR, Hanhardt M, Haselschwardt SJ, Hertel SA, Hogan DP, Horn M, Huang DQ, Ignarra CM, Ihm M, Jacobsen RG, Ji W, Kamdin K, Kazkaz K, Khaitan D, Knoche R, Larsen NA, Lee C, Lenardo BG, Lesko KT, Lindote A, Lopes MI, Manalaysay A, Mannino RL, Marzioni MF, McKinsey DN, Mei DM, Mock J, Moongweluwan M, Morad JA, Murphy ASJ, Nehrkorn C, Nelson HN, Neves F, O'Sullivan K, Oliver-Mallory KC, Palladino KJ, Pease EK, Pech K, Phelps P, Reichhart L, Rhyne C, Shaw S, Shutt TA, Silva C, Solovov VN, Sorensen Pet al., 2017, Chromatographic separation of radioactive noble gases from xenon, Astroparticle Physics, Vol: 97, Pages: 80-87, ISSN: 0927-6505

The Large Underground Xenon (LUX) experiment operates at the Sanford Underground Research Facility to detect nuclear recoils from the hypothetical Weakly Interacting Massive Particles (WIMPs) on a liquid xenon target. Liquid xenon typically contains trace amounts of the noble radioactive isotopes 85 Kr and 39 Ar that are not removed by the in situ gas purification system. The decays of these isotopes at concentrations typical of research-grade xenon would be a dominant background for a WIMP search experiment. To remove these impurities from the liquid xenon, a chromatographic separation system based on adsorption on activated charcoal was built. 400 kg of xenon was processed, reducing the average concentration of krypton from 130 ppb to 3.5 ppt as measured by a cold-trap assisted mass spectroscopy system. A 50 kg batch spiked to 0.001 g/g of krypton was processed twice and reduced to an upper limit of 0.2 ppt.

Journal article

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