Bubble Chamber Calibra-ons

Transcription

1 Bubble Chamber Calibra-ons E. Dahl, for PICO Collabora-on 1

2 E. Vázquez-Jáuregui I. Lawson M. Ardid, M. Bou-Cabo, I. Felis C. Amole, M. Besnier, G. Caria, G. Giroux, A. Kamaha, A. Noble D.M. Asner, J. Hall D. Baxter, C.E. Dahl, M. Jin, J. Zhang P. Bhattacharjee. M. Das, S. Seth S.J. Brice, D. Broemmelsiek, P.S. Cooper, M. Crisler, E. Behnke, H. Borsodi, O. Harris, R. Neilson W.H. Lippincott, E. Ramberg, A. LeClair, I. Levine, E. Mann, M.K. Ruschman, A. Sonnenschein J. Wells R. Filgas, I. Stekl F. Debris, M. Fines-Neuschild, C.M. Jackson, M. Lafrenière, J.I. Collar, M. Laurin, J.-P. Martin, D. Maurya, S. Priya A.E. Robinson A. Plante, N. Starinski, E. Dahl, 9/25/15, KICP V. Zacek S. Fallows, C. Krauss, P. Mitra K. Clark J. Farine, F. Girard, A. Le Blanc, R. Podviyanuk, O. Scallon, U. Wichoski 2

3 Outline Bubble Chamber Thermodynamics Nuclear Recoil Calibra-ons Charged Pions Low- energy neutrons High- energy neutrons Electron Recoil Calibra-ons When is an ER not just an ER? Scin-lla-ng bubbles 3

4 Bubble Chamber Basics Superheated Target CF 3 I, C 3 F 8, Par-cle interac-ons nucleate bubbles Cameras and acous-c sensors capture bubbles Chamber recompresses ater each event 4

5 Bubble Chamber Basics For interac-ons in this talk, response is BINARY bubble/no- bubble By the -me we hear a bubble, it s drawn 1 MeV from the fluid By the -me we see it, it s drawn 10 PeV 5

6 Bubble Chamber Thermodynamics Reaching the superheated state Superheated Liquid 6

7 Bubble Chamber Thermodynamics Consider the equilibrium state with a bubble: T l = T b (thermal equilibrium) µ l = µ b (chemical equilibrium) (so P b P vap ) P b P l = P s = 2σ / r c (mechanical equilibrium) P l, T l P s P b, T b Note, this is an unstable equilibrium 7

8 Bubble Chamber Thermodynamics What does it take to produce cri-cal bubble? 1.53 kev P l =30 psia, T l =14 o C = 3.19 kev total 1.81 kev kev P b = 89.7 psia r c =23.7nm Surface energy, Bulk energy, Reversible Work C 3 F 8 8

9 Bubble Chamber Thermodynamics What does it take to produce cri-cal bubble? Energy (heat) deposi-on > E T In a volume < r c 0 th order, dream scenario: Nuclear recoils with E r > E T make bubbles Electron recoils don t make bubbles 9

10 Nuclear Recoils beyond 0 th order TRIM simula-on (15 kev 19 F in CF 3 I) Nuclear recoils not all < r c, definitely not << r c Not all electronic stopping converted to local hea-ng (Inverse Lindhard effect) 10

11 Nuclear Recoil Efficiency Defini-on For each target fluid, need to measure set of probabili-es P X (E r E T ) that a recoil of energy E r and species X makes a bubble in a chamber at thermodynamic threshold E T Assump-ons: P X monotonic in E r, E T P X = 0 for E r < E T P high- A > P low- A at fixed E r, E T 11

12 Nuclear Recoil Calibra-ons: Threshold detector! Challenges Bubble Rate = de r P(E r ) x R(E r ) Efficiency Spectrum Cannot determine efficiency with single recoil spectrum High- energy recoils wash out sensi-vity near threshold 12

13 Nuclear Recoil Calibra-ons: Threshold detector! Challenges 1k bubbles / day max Tagged scaoering requires complete tagging (no wasted bubbles) Mul-ple nuclei with different kinema-cs 13

14 Nuclear Recoil Calibra-ons: Advantages! No electron sensi-vity! No shielding necessary with 9 Be(γ,n) sources Can work with charged beams directly (e.g. π - scaoering) Excellent 3- D posi-on reconstruc-on Take advantage of mul-ple scaoering 14

15 The CIRTE Experiment Phys. Rev. D 88, (2013) 12 GeV π CF 3 I E r = (pθ) 2 / 2M N 13.5 kev 127 I recoil = 4.7 mrad scaoer 0.7 mrad resolu-on (mul-ple Coulomb scaoering and pixel size) 15

16 Silicon Pixel Telescope at the Fermilab Test Beam Facility E. Dahl, 9/25/15, KICP 16

17 Silicon Pixel Telescope + Bubble Chamber 17

18 Voltage (au) Voltage (V) 1 CIRTE Event Telescope trigger Acoustic signal Time (ms) 0 Y position (mm) Upstream hits Downstream hits Z position (mm) CF 3 I 18

19 CIRTE Results Bubble nucleation fraction I F C Iodine equivalent recoil (kev Ie ) CF 3 I At E T =13.6 kev, P I- 127 consistent with step- func-on at E r =16.8 kev 19

20 Neutron Calibra-ons Mono- energe-c low- energy neutrons 51 V(p,n) 51 Cr Many very sharp (~.25 kev) resonances Neutrons from 4.8 to 119 kev 9 Be(γ,n) 88 Y, 207 Bi, 124 Sb 4.8 kev Phys. Rev. 100, 167 (1955) 82 kev 20

21 Neutron Calibra-ons Data on- and off- Fluorine resonances ENDF (and thus Geant4, MCNP) gets these resonances wrong (has them as isotropic) Fixed in: A. Robinson PRC 89, (2014) 21

22 Sample 51 V(p,n) data kev neutrons 40 kev neutrons Beam on bubble rate (bubbles / sec) Threshold (kev) No carbon turn- on, apparent fluorine turn- on Fluorine endpoints C 3 F 8 22

23 Absolute Normaliza-on of 51 V(p,n) Data Two 3 He counters recording neutron exposure in superheated state 1 fixed posi-on below 51 V target 1 in various posi-ons to measure angular distribu-on of emioed neutrons Simula-on must reproduce rela-ve rates in 2 3 He counters to include data Measure 51 Cr in target (27.7 day, 320- kev γ) Absolute neutron flux known to 7%- 11%, depending on neutron energy 23

24 AmBe in PICO- 2L High- mul-plicity events measure sensi-vity to low- energy recoils e.g. neutron stays in fluorine resonance for many few- kev scaoers C 3 F 8 24

25 Throw it all together C 3 F 8 Fit to piece- wise linear efficiency curves `kinks fixed at 0%, 20%, 50%, 80%, 100% Energy of kinks floats (10 free parameters) For WIMP limit, use most pessimis-c efficiency consistent with calibra-on data at 1- sigma Depends on WIMP mass, interac-on 25

26 Throw it all together C 3 F 8 CF 3 I PRELIMINARY Fit to piece- wise linear efficiency curves `kinks fixed at 0%, 20%, 50%, 80%, 100% Energy of kinks floats (10 free parameters) For WIMP limit, use most pessimis-c efficiency consistent with calibra-on data at 1- sigma Depends on WIMP mass, interac-on 26

27 Electron Recoils C 3 F 8 CF 3 I Many gamma energies, several genera-ons E. Dahl, of 9/25/15, detectors KICP 27

28 Electron Recoils C 3 F 8 CF 3 I But why are C 3 F 8 and CF 3 I so different? 28

29 Anomaly Discovered Gamma Rejection C Preliminary 3 F 8 gets CF 3 I gamma sensi-vity??? CYRTE 88 Y CYRTE 124 Sb C 3 F 8 CF 3 I Probability Threshold (kev) 29

30 Anomaly Verified Gamma Rejection Anomalous sensi-vity Reproduced Preliminary at Northwestern Y 124 Sb 137 Cs 207 Bi 241 Am Probability Cs Threshold (kev) 30

31 A common thread The C 3 F 8 chambers with high gamma sensi-vity all had poten-al for high- Z contaminants Tungsten residue from a thoriated welding rod test in the Northwestern chamber Are we seeing Auger cascades in high- Z nuclei? 31

32 A test for Tungsten 207 Bi source kev: 74% BR <- Photoabsorp-on candidate 570 kev: 98% 1064 kev: 75% If W- photoabsorp-on is culprit, 2mm lead will cut rate by order of magnitude 32

33 A test for Tungsten If W- photoabsorp-on is culprit, 2mm lead will cut rate by order of magnitude Background Subtracted Rate (events/s) Bi 208, unshielded Bi 208, unshielded Expected effect of shield on C 3 F 8 interactions Fe interactions W interactions Bi 207 shielded Threshold (kev) 33

34 Bubble Nuclea-on by Auger Cascades Auger cascades can lead to 10+ sub- kev electrons from the parent atom Vastly different track topology than you get from single high- energy electron Compton Scaoers and νe- >νe can leave inner shell vacancies, unlike 3 H decays. Thomas- Imel says this shouldn t maoer in xenon below 10 kevee, but worth checking 34

35 A Scin-lla-ng Xenon Bubble Chamber All the perks of a bubble chamber ER insensi-vity Easy 3D recon (no E- field req d) With scin-lla-on light for energy scale 550 o C&zone& Superheated&xenon& to&hydraulic&pressure&control& Photodetector& Camera& 5100 o C&zone& to&xenon&source& to&cold&head& 1 Year ago 35

36 A Scin-lla-ng Xenon Bubble Chamber All the perks of a bubble chamber ER insensi-vity Easy 3D recon (no E- field req d) With scin-lla-on light for energy scale Camera Port Warm Flange Mirror Xenon (Target Fluid) Cold Flange Bellows 4 months ago 36

37 A Scin-lla-ng Xenon Bubble Chamber Possible new tool for calibra-ons Inverse Lindhard measurement Photoneutrons without shielding (S1 only) Other ideas? 3 weeks ago E. Dahl, 9/25/15, KICP Assembling*the*detector* 37

38 Summary Nuclear Recoils Nuclea-on probability determined by Pion scaoering Mono- energe-c neutrons with absolute rate calibra-on Bubble mul-plicity Close to thermodynamic limit when tracks are small Electron Recoils Not all electron recoils are equal Auger cascades give much higher bubble nuclea-on probability than beta s or valence Compton scaoers 38