1. D 3 - Directional Dark Matter Detector Sven Vahsen (U. Hawaii)1 Berkeley Lab Hawaii LBNL Hawaii Investigating feasibility of directional DM search w/ micro-pattern gas detectors Advantage: 3D recoil tracking, very high S/N, single electron sensitivity Small (1-60 cm 3 ) prototypes built at LBNL and U. Hawaii Ongoing since ~Fall 2010 D 3 - micro

2. charge amplification w/ CERN GEMs charge Detection with ATLAS pixel chips custom Al metallization perhaps electrostatic charge focusing D 3 Detector Concept P.M. Lewis, S.E. Vahsen, I.S. Seong, M.T. Hedges, I. Jaegle, T.N. Thorpe, Absolute position measurement in a gas time projection chamber via transverse diffusion of drift charge, Nucl. Instrum. Meth. A 789 (2015) S.E. Vahsen, M.T. Hedges, I. Jaegle, S.J. Ross, I.S. Seong, T.N. Thorpe, J. Yamaoka, J.A. Kadyk, M. Garcia-Sciveres, 3-D tracking in a miniature time projection chamber, Nucl. Instrum. Meth. A 788 (2015) S.E. Vahsen, K. Oliver-Mallory, M. Lopez-Thibodeaux, J. Kadyk, M. Garcia-Sciveres, Tests of Gases in a Mini-TPC with Pixel Chip Readout, Nucl. Instrum. Meth. A, 738 (2014) T. Kim, M. Freytsis, J. Button-Shafer, J. Kadyk, S.E. Vahsen and W. A. Wenzel, Readout of TPC tracking chambers with GEMs and pixel chip, Nucl. Instrum. Meth. A 589, 173 (2008) S. E. Vahsen, H. Feng, M. Garcia-Sciveres, I. Jaegle, J. Kadyk, Y. Nguyen, M. Rosen, S. Ross, T. Thorpe, J. Yamaoka, The Directional Dark Matter Detector, Proceedings of the 3rd International conference on Directional Detection of Dark Matter (CYGNUS 2011), http://arxiv.org/abs/1110.3401

3. Detectors at U. Hawaii µD 3 (~1cm 3 ) 2011-2013 2016 (planned) (planned, still unfunded) mD 3 (~10 liters)D 3 (~1m 3 ) 1 pixel chip 16 pixel chips~400 pixel chips 20132014 2015 2 x 60 cm 3 8 x 40 cm 3 ~ 20 cm 3

4. Latest detector: ~40 cm 3 TPC w/ Field Cage - building eight, two completed Latest ATLAS FE-I4 50 x 250 µm pixels 20.3 by 19.2 mm active Pixel chip: Directional fast neutron detector. Small footprint enabled by Parylene coating on inside of pressure vessel

5. Events – 2D Neutron recoil event: Cf-252 source outside vacuum vessel, pointed at z=8 cm (middle of TPC) neutron charge Figures show 2-D projection of ionization density, measured w/ 2x2 cm pixel chip As a consequence of high gain low threshold, and low noise, the rate of noise hits is negligeable no noise hits! CYGNUS 2015Sven Vahsen (U. Hawaii)5

6. Three Superimposed Events – 2D CYGNUS 2015Sven Vahsen (U. Hawaii)6 Experimental data No offline noise suppression He:C0 2 gas (70:30) at p=1atm x-ray conversion nuclear recoil induced with D-D neutron generator α-particle from Po-210 calibration source 2.03 cm 1.92 cm

7. Ionization cloud from He-recoils, measured in 3D each colored block represents 50x250x250 μm 3 color: ionization density (green=highest, red=lowest) Fill gas: He:C0 2 (70:30) at p=1atm Expect directionality for ~keV recoils in low-pressure gas Nuclear Recoil Events – 3D ~1 MeV ~25 keV ee

8. What limits the Readout Plane Resolution? Colloquium @ UH ManoaSven Vahsen8 Point resolution for short pixel dimension not limited by detector segmentation, but by diffusion internal to the readout plane. Don’t need much smaller pixels.

9. What Limits The Energy Resolution? Colloquium @ UH ManoaSven Vahsen9 Good gain resolution for MeV-scale signals, adequate even for few-keV signals!  Expect to achieve good head-tail identification, perhaps even in keV range ArC0 2 at p=1atm Limited by gas ionization & avalanche processes Limited by analog PHA electronics PHA T. Thorpe

10. Angular resolution versus “track size” Colloquium @ UH ManoaSven Vahsen10 Angular resolution can be predicted analytically from point resolution. Agrees well with measurement. Allows extrapolation to other energies and gas pressures I. Seong Alpha particles Analytical “prediction”:

11. BACKUP CYGNUS 2015Sven Vahsen (U. Hawaii)11

12. D 3 Team at U. Hawaii and Berkeley Lab John Kadyk Maurice Garcia-Sciveres Kelsey Oliver-Mallory (UC Berkeley Student) Sven E. Vahsen Michael Hedges Graduate Student Ilsoo Seong Graduate Student Thomas Thorpe Graduate Student Sven Vahsen (U. Hawaii)12 Mayra Lopez-Thibodeaux (UC Berkeley Student) Kamaluoawaiku Beamer Undergraduate Student (+rotating group) Peter Lewis Postdoc Josh Murillo Graduate Student

13. The Case for Low Track Energy Threshold Preliminary evaluation: 3-m 3 detector could achieve directional sensitivity to (controversial) ~10 GeV WIMPS Golden scenario - if DAMA/LIBRA were due to WIMPs: – observe ~1000s of non- directional events (can observe yearly oscillation) – use subset (~100) of these to search for daily directional oscillation, to determine if BG or WIMPs http://arxiv.org/abs/1110.3401 D 3 Preliminary Estimated sensitivity to spin-independent WIMP- nucleon scattering, 3-m 3 directional dark matter detector, running for 3 years with 33 cm drift length and CF 4 gas, for four different track reconstruction thresholds and for non-directional analysis. CYGNUS 2015Sven Vahsen (U. Hawaii)13 Superior S/N & track energy treshold of order 10 keV crucial for detecting 10 GeV WIMPS!

14. D 3 Micro: 1 cm 3 (2011) 1 cm 3 CYGNUS 2015Sven Vahsen (U. Hawaii)14 ATLAS FE-I3 50 x 400 µm pixels 7.4 by 11.0 mm active Pixel chip: cathode GEM foil circuit board that holds pixel chip

15. D 3 Micro: Example of Events Cosmic ray events to demonstrate tracking w/ low track-energy threshold each block: 50x400x400 μm 3. Color shows measured ionization density hit threshold ~ 30eV. Note absence of noise hits! ArCO 2 (70:30) p=1 atm HeCO 2 (70:30) p=1 atm E~ 2 keV E~ 1 keV

16. Energy Resolution – Initial Problems In this first prototype, the energy resolution observed with the pixel chip was however much worse than gain resolution Due to defects in the metallization layer Now resolved July 2013 Sven VahsenARI Grantees Conference16

17. D 3 Micro-5: ~2.5 cm 3 (2013) CYGNUS 2015Sven Vahsen (U. Hawaii)17 ATLAS FE-I3 50 x 400 µm pixels 7.4 by 11.0 mm active Pixel chip:

18. Cf-252 Source Present Source Absent D 3 Micro-5: 3D Directional Neutron Detection 27-sigma evidence for “neutron wind” in our lab! Recoils point back to source, in 3D. He-recoil measured in HeC0 2 gas at p=1atm L ~ 5 mm E ~ 350 keV/c 2 Incoming neutron Scattered neutron Nuclear recoil neutron source Mean direction of nuclear recoils corresponds to neutron source location

19. D 3 Micro-20: 20 cm 3 (2013) CYGNUS 2015Sven Vahsen (U. Hawaii)19

20. CYGNUS 2015Sven Vahsen (U. Hawaii) ~60 cm 3 TPC w/ Field Cage (2014) Latest ATLAS FE-I4 50 x 250 µm pixels 20.3 by 19.2 mm active Pixel chip: 20 Prototype fast neutron detector. Small footprint enabled by Parylene coating on inside of pressure vessel CYGNUS 2015Sven Vahsen (U. Hawaii)20

21. Final Micro-TPC Prototype Design Sensitive volume Charge amplification (GEMs) Field cage Charge Detection (Pixel Chip) Aluminum vacuum vessel CYGNUS 2015Sven Vahsen (U. Hawaii)21

22. Micro-TPC Assembly and Testing in Hawaii Clean Room CYGNUS 2015Sven Vahsen (U. Hawaii)22

23. Internal Calibration Sources Three Po-210 alpha-particle sources source 1source 2source 3 in-situ, time-dependent, and z-dependent calibration of energy scale and detailed response to helium recoils CYGNUS 2015Sven Vahsen (U. Hawaii)23

24. Long Term Stability Test Continuous operation and DAQ for >1 month, summer 2014 Flow-rate controller and pressure regulator Excellent gain stability, at ~1% level per week, pre- calibration, during stable lab conditions, as shown on right Can be calibrated out with the calibration source data time (one week total) ionization measured source 1 source 2 source 3 Sufficient stability to observe annual oscillation in WIMP rate / spectrum CYGNUS 2015Sven Vahsen (U. Hawaii)24

25. Angular and Energy Resolution – 2cm alpha tracks Sub-1-degree angular resolution even after ~15 cm drift. Energy resolution now comparable to gain resolution. CYGNUS 2015Sven Vahsen (U. Hawaii)25 I. Seong

26. Absolute Position Measurement Measurement of charge-profile (not width) of track, enables accurate measurement of transverse diffusion  obtain absolute position in drift direction P.Lewis CYGNUS 2015Sven Vahsen (U. Hawaii)26

27. Absolute Position Measurement December 18, 2014US Belle II Project Mini Review27 2-mm track segments. 8-mm track segments.  enables 3D-fiducialization, even for very short track, presumably for more or less any gas Charge profile analysis also enables “Energy Recovery” (unpublished) P.Lewis