The DRIFT experiment: Recent results from the DRIFT-IId detector James Battat Wellesley College [for the DRIFT collaboration] CYGNUS Oxy 2015 June 2 nd

Overview of talk CS 2 as negative ion drift Martoff et al. NIMA, 400 (2000); Snowden-Ifft, Martoff, Burwell, PRD (2000). DRIFT’s successful quest to reduce backgrounds Currently operating background-free Snowden-Ifft, Rev. Sci. Instrum (2014) [DRIFT collab.] Battat et al., JINST, 9 P11004 (2014) [DRIFT collab.] Battat et al., NIMA 794 (2015) 2014 SD-proton limit: 1 pb at 100 GeV/c 2. [DRIFT Collab.], Battat et al., arXiv: , submitted to Phys. of Dark Universe Steve Sadler, PhD Thesis Sheffield University, 2014 Additional improvements give preliminary result of σ SD-p ~0.3 pb 6/2/2015James Battat, Wellesley College, CYGNUS20151

Occidental College Dan Snowden-Ifft - PI Jean-Luc Gauvreau Chuck Oravec Alex Lumnah Nick Waldram Colorado State University John Harton – PI Jeff Brack Dave Warner Alexei Dorofeev Fred Shuckman II Sheffield University Neil Spooner – PI Ed Daw – PI Matt Robinson Dan Walker Steve Sadler Andrew Scarff Anthony Ezeribe Frederic Mouton Trevor Gamble Directional Recoil Identification From Tracks 2 James Battat, Wellesley College, CYGNUS2015 6/2/2015 University of New Mexico Dinesh Loomba - PI Michael Gold – PI John Matthews - PI Eric Lee Eric Miller Nguyen Phan Randy Lafler Joshua Martin The University of Edinburgh Alex Murphy – PI Wellesley College James Battat – PI University of Hawaii Sven Vahsen – PI Tom Thorpe Josh Murillo Boulby Laboratory Sean Paling – PI Emma Meehan Louise Yeoman Chris Toth

DRIFT in Boulby: 2805 m.w.e. 3 James Battat, Wellesley College, CYGNUS2015 Mei & Hime [astro-ph/ ] For scope of work at Boulby, see talk by Chris Toth, Thursday 14:30. 6/2/2015 Operated by the UK’s Science & Technology Facilities Council (STFC) in partnership with the mine operators ICL

Negative ion formation 4James Battat, Wellesley College, CYGNUS2015 Nuclear Recoil WIMP e-e- e-e- e-e- e-e- e-e- e-e- e-e- E-field Drift direction Mean electron capture distance is a few hundred microns Martoff et al., NIMA, 440 (2000) Snowden-Ifft, et al., PRD, 61, (2000) Snowden-Ifft & Gauvreau, Rev. Sci. Instrum., 84, (2013) 6/2/2015

Transport of CS 2 negative ions Diffusion is ~ thermal (both transverse and longitudinal) low diffusion increases active volume per readout area Drift speeds are ~5 cm/msor ~20 us/mm 5James Battat, Wellesley College, CYGNUS2015 Snowden-Ifft & Gauvreau, Rev. Sci. Instrum., 84, (2013) [arXiv: v2] 6/2/2015

Negative ion gas mixtures Ar:CH 4 :CS 2, Xe:CS 2, CF 4 :CS 2, CF 4 :O 2 :CS 2 … Martoff et al., NIMA 440 (2000) Lightfoot et al., Astropart. Phys. 27 (2007) CS 2 is not the only negative ion gas Nitromethane (CH 3 NO 2 ) [Martoff et al., NIMA 598 (2009)] SF 6 [see Nguyen Phan’s talk Thr., 13:30] 6/2/2015James Battat, Wellesley College, CYGNUS20156

Some DRIFT detector nomenclature 7James Battat, Wellesley College, CYGNUS2015 DRIFT-IId 0.8 m 3 Demonstrated 2 pb sensitivity in 2012 Has since been upgraded and is currently running background-free (texturized thin-film cathode, and 3D fiducialization) DRIFT-IIe 0.8 m 3 engineering prototype for DRIFT-III Currently at Occidental College. DRIFT-III 24 m 3 (Proposed) D-HD DRIFT-HD 0.25 m 3 high spatial-resolution (Proposed) 6/2/2015

DRIFT-IId geometry 6/2/2015James Battat, Wellesley College, CYGNUS20158 Dimensions in mm Fiducial volume is 0.8 m Image from Burgos et al., NIMA 584 (2008)

Grid wires -2.8kV 100 um diam. DRIFT-IId geometry 6/2/2015James Battat, Wellesley College, CYGNUS20159 Left MWPCRight MWPC Cathode -32kV z=0 z=50 cm z=0 900

6/2/2015James Battat, Wellesley College, CYGNUS Image from M. Pipe PhD Thesis, U. Sheffield, 2011 … 448 anode wires … Heavy grouping, low channel count 100% spatial ambiguity (8-wire = 16 mm periodicity) DRIFT readout

The War on Backgrounds 2005:500 evt/day 2012:130 evt/day(material selection) 2014: 1 evt/day(0.9 um thin-film cathode) 2014: 0 evt/day(z-fiducialization) 6/2/2015James Battat, Wellesley College, CYGNUS See talk by Eric Miller, Wed., 13:30

z-fiducialization: differential drift speeds 6/2/2015James Battat, Wellesley College, CYGNUS Drift direction Proportionality constant can be measured for various gas mixtures, or calibrated in-situ. MWPC

z-fiducialization: limitations 6/2/2015James Battat, Wellesley College, CYGNUS Po-210 Snowden-Ifft, Rev. Sci. Instrum (2014). Data from an R&D vessel, not DRIFT-IId

DRIFT-IId: some numbers CS 2 :CF 4 :O 2 30:10:1 Torr Mass ofF:40g/0.8m 3 C:18g/0.8m 3 S:96g/0.8m 3 30 keVr F recoil = 1 mm range CS 2 - drift speed ~5 cm/ms. (10 ms for full 50 cm drift, 20us/mm) Gas gain ~1000 Source-free running for 46.3 live days Fe-55 calibrations every 6 hours Cf-252 neutron calibration 5 runs, 3.2 live days 14James Battat, Wellesley College, CYGNUS20156/2/2015

Events in DRIFT 6/2/2015James Battat, Wellesley College, CYGNUS RG = Right grid (1 – 8 and sum) RVG = Right veto (grid) RVA = Right veto (anode) RA = Right anode (1 – 8 and sum) Any anode channel > 30 mV triggers readout of all channels. Raw trigger rate ~ 1 Hz Adverse effect on E thresh 50% efficiency at ~50 keVr F Improved trigger implemented 50% eff. at ~20 keVr F

Events in DRIFT 6/2/2015James Battat, Wellesley College, CYGNUS RG = Right grid RVG = Right veto (grid) RVA = Right veto (anode) RA = Right anode Right MWPC, Anode #7 Line

Data processing 6/2/2015James Battat, Wellesley College, CYGNUS Stage I cuts E recon Bkg rejection z recon Signal conditioning Raw triggers Noise filtering, undershoot removal, saturation cut

Data processing 6/2/2015James Battat, Wellesley College, CYGNUS xy-fiducialization (veto above threshold) Temporal ROI cut (+/- 700 us) Cathode-crossing events (hits in both TPCs) Multiples (non-contiguous hits) Maximum range (all 8 anode channels R y >16 mm) Impulse charge deposition (risetime < 3us) Stage I cuts E recon Bkg rejection z recon Raw triggers Signal conditioning

Data processing 6/2/2015James Battat, Wellesley College, CYGNUS E recon Bkg rejection z recon Raw triggers Signal conditioning Stage I cuts

Data processing 6/2/2015James Battat, Wellesley College, CYGNUS E recon Bkg rejection z recon Raw triggers Signal conditioning Stage I cuts Compute event energy in mV*us Sum up waveform integrals for all anode channels above an analysis threshold (9 mV). Convert to keV ee (equivalently NIPs) mV*us to keV ee via 55 Fe calibration (every 6h, stable to 4%) keV ee to NIPs via W=25.2 eV * Convert to keV r Use [Hitachi 2008] prediction. For CS 2 :CF 4 quenching measurements, see talks by Eric Miller (Wed., 13:30) and Alex Lumnah (Thr., 14:00) * W not yet measured for CS 2 :CF 4 :O 2 mixture, but expect ~1% change from CS 2 :CF 4, which has been measured [P&S 2009]. [Hitachi 2008]Hitachi, Radiat. Phys. Chem. 77 (10–12) (2008) [P&S 2009]Pushkin & Snowden-Ifft, NIMA 606 (2009)

Data processing 6/2/2015James Battat, Wellesley College, CYGNUS Require 3 peaks, evenly spaced E recon Bkg rejection z recon Raw triggers Signal conditioning Stage I cuts dt ~ 150 us (S to I) Z ~ (0.24 cm/us)*dt ~ 36 cm I peak width is ~ 50 us, so z-recon gets hard below z ~10 cm.

Cathode RPR/LEAs 6/2/2015James Battat, Wellesley College, CYGNUS201522

Detection efficiency post-Stage I 6/2/2015James Battat, Wellesley College, CYGNUS % at ~50 keV 50% at ~20 keV

Nuclear Recoil Detection Efficiency Map 6/2/2015James Battat, Wellesley College, CYGNUS201524

DRIFT’s 2015 SD-proton limit 6/2/2015James Battat, Wellesley College, CYGNUS NEWAGE (2015) PICO (2015) DRIFT (2012) DRIFT (2015) DMTPC (2011)

Room for improvement Improved trigger to capture lower energy events Factor of ~2 in threshold Improve efficiency at high-z z-reconstruction does not rely on S-peak Gas circulation to maintain O 2 partial pressure Minority peak ionization is strongly O 2 dependent. Can we do better at low z (z<10cm)? Will new backgrounds appear? 6/2/2015James Battat, Wellesley College, CYGNUS201526

Efficiency Map (prelim.) 6/2/2015James Battat, Wellesley College, CYGNUS201527

Preliminary analysis shows 0.3 pb 6/2/2015James Battat, Wellesley College, CYGNUS DRIFT (2015b, preliminary)

Events passing cuts 6/2/2015James Battat, Wellesley College, CYGNUS201529

Summary A 1 pb limit is on the arXiv: Since then, upgrades to the detector and analysis have improved the reach by another factor of ~3 to give σ SD-p ~ 0.3 pb Have ~65 live-days in-hand (and counting). 6/2/2015James Battat, Wellesley College, CYGNUS201530

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Quenching 6/2/2015James Battat, Wellesley College, CYGNUS201532

6/2/2015James Battat, Wellesley College, CYGNUS201533

DAQ has a high-pass filter To get rid of 50 Hz mains noise. (1/50Hz = 20ms = 20000us) For C=2200 pF, R=50 Ohm, tau=RC= 0.1us (see M. Pipe’s thesis, page 61). 6/2/2015James Battat, Wellesley College, CYGNUS201534

Waveform conditioning Frequency filtering – 55 kHz noise notch filter (HV supply) – 50 Hz line noise (subtract sine fit) Undershoot correction – Shaping electronics (4 us shaping time) cause undershoot Analysis threshold is 9 mV (trigger threshold was 30 mV). What is waveform baseline RMS? 6/2/2015James Battat, Wellesley College, CYGNUS201535

DRIFT readout 6/2/2015James Battat, Wellesley College, CYGNUS Anode wires …

Grid 512 wires 100 um diameter Anode 512 wires 20 um diameter MWPC 3 planes 1 cm gaps 6/2/2015James Battat, Wellesley College, CYGNUS201537

6/2/2015James Battat, Wellesley College, CYGNUS Passes cuts on: xy fiducialization Risetime Multiples Fails cut because: Cathode-crossing Range too long (all anode lines hit) ROI cut RATE OF ALPHAS???

Background rejection Spark cut Ratio of ionization in minority carriers region to total ROI ionization “Ringer” cut Require comparable ionization on anodes and grid 6/2/2015James Battat, Wellesley College, CYGNUS201539

Stage I cuts xy-fiducialization (veto above threshold) Temporal ROI cut (+/- 700 us) Cathode-crossing events (hits in both TPCs) Multiples (non-contiguous hits) Maximum range (all 8 anode channels R y >16 mm) Impulse charge deposition (risetime < 3us) 6/2/2015James Battat, Wellesley College, CYGNUS201540

Energy reconstruction Compute event energy in mV*us Sum up waveform integrals for all anode channels above an analysis threshold (9 mV). Convert to NIPs (equivalently keV ee ) Calibration constant derived from frequent 55 Fe calibrations studies – stable to ~4% over experiment. Also: W=25.2 eV * Convert to keV r Use [Hitachi 2008] prediction. For CS 2 :CF 4 quenching measurements, see talks by Dinesh Loomba (DAY, TIME) and Alex Lumnah (DAY, TIME) * W not yet measured for CS 2 :CF 4 :O 2 mixture, but expect ~1% change from CS 2 :CF 4, which has been measured [P&S 2009]. [P&S 2009]Pushkin & Snowden-Ifft, NIMA 606, 2009 [Hitch 2008]Hitachi, Radiat. Phys. Chem. 77 (10–12) (2008) 6/2/2015James Battat, Wellesley College, CYGNUS201541

Transport of CS 2 negative ions Diffusion is ~ thermal (both transverse and longitudinal) Drift speeds are ~5 cm/msaka ~20 us/mm “low-field” approximation hold even at 580 V/cm 42James Battat, Wellesley College, CYGNUS2015 Snowden-Ifft & Gauvreau, Rev. Sci. Instrum., 84, (2013) [arXiv: v2] 6/2/2015

Grid 552 wires, 448 fid. 2 mm pitch 100 um diameter Anode 552 wires, 448 fid. 2 mm pitch 20 um diameter MWPC 3 planes 1 cm gaps z=0 z=50 cm z=0 DRIFT-IId geometry 6/2/2015James Battat, Wellesley College, CYGNUS

TO DO Dates for new limit run (July to October 2014) Verify gas gain = 1000 Why is 55-day efficiency so high at z~50cm? (used to be 10-30%, is now 25-90%)? Capacitance of ONE anode wire? Cap. when grouping 56 of them into one preamp? Rates of events that get cut??? What is alpha rate? ~1/4 Hz. Why are so many anode wires needed for the veto? (43 on each side, plus 9 guard wires on each side). What is new triggering scheme (integral?) 18 us boxcar averaging for trigger. New threshold is 15 mV. 50% at 500 NIPs Validation that waveform filtering (notch filter, 50 Hz, undershoot removal) preserve event quantities like energy, head tail, etc.? Why integrate waveforms (vs. take amplitude) for NIPs? Isn’t it already integrated by electronics? Check collaboration slide Fix “Boulby Mine” slide. Fe e- 6/2/2015James Battat, Wellesley College, CYGNUS201544

Events passing cuts 6/2/2015James Battat, Wellesley College, CYGNUS201545