Detectors for particles and radiation Advanced course for Master students

1. Detectors for particles and radiation Advanced course for Master students Spring semester 2010 S7139 5 ECTS points Tuesday 10:15 to 12:00 - Lectures Tuesday 16:15 to 17:00 - Exercises

2. Detectors for particles and radiation

3. High density (1.0-1.7 g/cm2) • High charge mobility • Long charge lifetime • Scintillation Cryogenic noble liquids as the detector medium • Low operating temperature (70-90K) • Relatively high Wi value -> medium Fano factor • Scintillation in deep UV region (VUV) • Ionization • Recombination • Charge drift • Charge diffusion • Charge attachment on impurities • Scintillation

4. Cryogenic noble liquids as the detector medium

5. neg. high voltage plane particle track E liberated e- gating plane Z (e-drift time) cathode plane anode plane Y pads X Induced charge on the plane TPC – Time Projection Chamber • Time Projection Chamber • full 3D track reconstruction: • x-y from wires and segmented • cathode of MWPC (or GEM) • z from drift time • momentum resolution • space resolution + B field • (multiple scattering) • energy resolution • measure of primary ionization

6. Ionization in cryogenic noble liquids Example LAr: ρ= 1.4 g/cm2 @ 87K dE/dX ≈ 2MeV/cm for M.I.P. Wi = 23.6 eV/e- Q0 ≈ 8500 e/mm ≈ 1.4 fC/mm The charge is produced along the track in a dense column, The charge density depends in dE/dX -> different for light and heavy particles.

7. Charge in TPC with electric field Response to a primary ionization Primary ionisation Q0 Recombination losses q0=A*Q0 Attachment losses q=q0e -(D/λ) Particle E I- Ar+ e- I- I- Ar+ e- e- D, drift distance +V

8. Charge recombination in Cryogenic liquids : box model Q0 - primary ionization charge α – linear size of the charge “box” [cm] N0 – number of electrons in the box Kr – recombination rate constant [cm3/s] u- - electron mobility [cm2/Vs] E – electric field [V/cm]

9. Ionization signal vs E Charge recombination in LAr: box modelfor M.I.P (electrons)

10. Ionization signal vs E Charge recombination in LAr: box modelfor H.I.P (3 MeV alpha-particle)

11. 3 MeV alpha Energy resolution in Cryogenic liquids FLAR ≈ 0.1 – rather good

12. The Foundation: • A. Einstein, Über die von der molekularkinetischen Theorie geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen, Annalen der Physik322(1905) 549. (see p. 555 bottom) • M. von Smoluchowski, Zur kinetischen Theorie der Brownschen Molekularbewegung und der Suspensionen, Annalen der Physik21 (1906) 756. The Relationship Between Drift and Diffusion They found that for particles (x) in thermal equilibrium with a medium (M), the diffusion constant, mobility, and temperature were related: The Einstein–Smoluchowski Ratio If thermal equilibrium is not obtained (as in drift in high E fields), we can use the E-S ratio to define an electron energy: Note that the mean electron energy differs from this energy: Slide 3 of 12

13. Diffusion of Electrons in Liquid Argon “Leckner” points (triangles) are plotted at 2/3 of the calculated mean electron energy obtained from a solution to the Boltzmann transport equation in liquid Ar. See Table I in Lekner, PR. 158 (1967) 130. At thermal equilibrium kT=0.0075 eV Slide 4 of 12

14. The essence, from Parker and Lowke: If the electron collision frequency increases with energy, then the leading edge of the electron swarm has a reduced mobility because it has a higher-than-average electron energy and therefore higher collision rate. Conversely for the trailing edge, and the swarm is “compacted” along the drift direction. From Skullerud: Diffusion of Electrons in Strong Electric Fields Is Not Isotropic mean free path independent of velocity: collision rate proportional to a power of velocity: Theory – Boltzmann Transport Equation

15. Highly Selected Literature: • M.H. Cohen and J. Leckner, Theory of hot electrons in gases, liquids, and solids, PR 158 (1967) 305. • J. Lekner, Motion of electrons in liquid Argon, Phys. Rev. 158 (1967) 130. • B.M. Smirnov, Kinetics of electrons in gases and condensed systems, Phys.-Uspekhi 45 (2002) 1251. • V.M. Atrazhev and I.V. Timoshkin, Transport of electrons in atomic liquids in high electric fields, IEEE Trans. on Dielectrics 5 (1968) 450. Theory of Transport of Electrons in Non-polar Liquids In liquids the theory is more complex than in gases because the scattering of electrons occurs from correlations of atoms and from density fluctuations – one result is that the cross section and therefore the mobility is higher in liquid. Slide 7 of 12

16. Calculations and measurements of mobility and electron temperatures for liquid argon near the triple point and near the critical point Theory of Atrazhev and Timoshkin Mobility data is from Huang and Freeman and from H. Schnyders, et al. Slide 8 of 12

17. Interpolated to normal boiling point from A&T theory Transverse and Longitudinal Diffusion in LAr At 500 V/cm we find: DT=16.3 cm2/s, DL=6.2 cm2/s from theory;

18. Charge in TPC with electric field Response to a primary ionization Primary ionisation Q0 Recombination losses q0=A*Q0 Attachment losses q=q0e -(D/λ) Particle E I- Ar+ e- I- I- Ar+ e- e- D, drift distance +V

19. Q=Q0exp(t/t0) Lifetime t0 is defined by the impurity type and concentration Charge attachment losses : electronegative impurities Practical for LAr: τ[mcs]= 300/ρ[ppb]

20. Liquefied noble gases scintillation Liquefied noble gases: LAr, LXe, LKr Also here one finds 2 time constants: from a few ns to 1 ms.

21. Liquefied noble gases scintillation

22. Liquefied noble gases scintillation

23. Liquid Argon TPC (ICARUS) • Electronic Bubble chamber • Planes of wires (3mm pitch) widely separated (1.5m) 55K readout channels! • Very Pure Liquid Argon • Density: 1.4, Xo=14cm lINT =83cm • 3.6x3.9x19.1m3 600 ton module (480fid)

24. ICARUS TPC module

25. Cryogenic liquids dE/dx(mip) = 2.1 MeV/cm T=88K @ 1 bar We≈24 eV Wg≈20 eV Charge recombination (mip) @ E = 500 V/cm ≈ 40%

26. Liquid Argon TPC • Because electrons can drift a long time (>1m!) in very pure liquid argon, this can be used to create an “electronic bubble chamber” Raw Data to Reconstructed Event

27. AB K+ µ+ BC Bethe-Bloch : particle ID by energy deposition K+ e+ • From a single event, see dE/dx versus momentum (range) B µ+ C A Question: how would This look different for a p→m event? Run 939 Event 46

28. _ -  e- +  e +  Examples of Liquid Argon Events e-, 9.5 GeV, pT=0.47 GeV/c • Lots of information for every event… • Primary t tag: • edecay • Exclusive t tag: • r decay • Primary Bkgd: Beam ne CNGS  interaction, E=19 GeV e-,15 GeV, pT=1.16 GeV/c Courtesy André Rubbia Vertex: 10,2p,3n,2 ,1e- CNGS e interaction, E=17 GeV

29. p0 identification in Liquid Argon One photon converts to 2 electrons before showering, so dE/dx for photons is higher… Imaging provides ≈210-3 efficiency for single p0 1 π0 (MC) cut Preliminary <dE/dx> MeV/cm

30. Oustanding Issues Giant Liquid Argon Time Projection Chamber • Do Simulations agree with data (known incoming particles) • Can a magnetic field be applied • Both could be answered in CERN test beam program • Is neutral current rejection that good? • How large can one module be made? • What is largest possible wire plane spacing? Several R&D Efforts world-wideworking to get >10kton detectors “on the mass shell”

31. Detector Tank based on Industrial Liquefied Natural Gas (LNG) storage tanks Many large LNG tanks in service. excellent safety record

33. Cryogenic liquids charge readout

35. Filling the tank with LAr • The “Village water tank” has a volume the same as ~1,000 tons of liquid argon (1.40 g/cm3). • It was part of the village of Weston. • The intention is to use it to challenge models of purging tanks with a “piston” of argon gas. • Question: How does sunshine mess up the measurement? 1 kton represents the smallest “quantum” David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University Slide 35

36. Filling the tank with LAr Test of purging a volume from atmosphere: insert Argon gas at bottom of tank over large area at low velocity; the Argon introduced being heavier than air will act as a piston and drive the air out of the tank at the top; fewer volume changes than simple mixing model will achieve a given reduction in air concentration. gas out to PPM Monitor `O2 Monitor' tank volume = 157 cf tank cross section = 19 sf flow rate ~ 73.2 cf/h (reading for air was 86 scfh) climb rate ~ 3.8 f/h WASHED TANK 99 ins 48 ins `O2 Monitor' 24 ins diffuser argon gas in 59 ins David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University Slide 36

37. Filling the tank with LAr to 100 ppm (reduction of 2,000) takes 6 hrs = 2.6 volume changes (cf simple mixing, which predicts ln(2000) = 7.6 volume changes) David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University

38. Filling the tank with LAr David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University

39. Filling the tank with LAr David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University

40. Filling the tank with LAr David Finley / Liquid Argon TPC Workshop / July 11, 2006 @ Yale University

41. LAR TPC R&D at LHEP: • Big Argontube TPC: main goal to test long (6m) charge drift • Medium TPC: test bench for laser calibration and purity measurements • Small TPC: R&D on novel media (Lar+N), R&D on readout • Micro TPC: R&D on charge readout

42. LAR TPC R&D at LHEP: Large TPC: fiducial volume 350 l Argon volume 1000 l

43. LAR TPC R&D at LHEP: Medium TPC: fiducial volume <10 l Argon volume 60 l

44. LAR TPC R&D at LHEP: Small TPC: fiducial volume 200 cm3 Argon volume 40l

45. LAr purity measurements with UV laser CCD Camera Nd-YAG laser Z Coordinate Z=Dt x Photo diode Read-out plane Dt 64 wires each plane E1= 1 kV/cm Dt Dx Drift time

46. LAR TPC R&D at LHEP: Micro TPC: fiducial volume 3000 cm3 Argon volume 4l

47. High Field-Induced Emission readout R&D at LHEP: HFIE detectors based on MAPD High Field-Induce light Emission – Synergy with large LAR TPC R&D (“Argontube” detector ) LAr

48. Some literature to read about LAr TPC • W. Walkowiak, Drift velocity of free electrons in liquid argon, NIM A449 (2000) 288. • S. Amoruso, et al., Analysis of the liquid argon purity in the ICARUS T600 TPC, NIM A516 (2004) 68. • S.S-S.Huang and G.R. Freeman, Electron transport in gaseous and liquid argon: effect of density and temperature, Phys. Rev. A24 (1981) 714. • H. Schnyders, et al., Electron drift velocities in liquified argon and krypton at low electric field strengths, Phys. Rev. 150 (1966) 127. • E. Shibamura, et al., Ratio of diffusion coefficient to mobility for electrons in liquid argon, Phys. Rev. A20 (1979) 2547. (many fields > 1.5 kV/cm) • S.E. Derenzo, LBL Physics Note No. 786 (1974) unpublished . (at 1.4 & 2.7 kV/cm, large error bars?) • S.E. Derenzo et al., Test of a liquid argon ion chamber with a 20mm RMS resolution, NIM 122 (1974) 319 . (at 2.7kV/cm only)