1. GSI 9Feb09 NMI3 – Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy, Joint Research Activity (JRA8): MUON-S. Contract: RII3-CT-2003-505925 A. Stoykov, R. Scheuermann, K. Sedlak Application of G-APDs in Muon Spin Spectroscopy 1 G-APD + plastic scintillator: some results on the time resolution 2

2. G-APDs in  SR Development of G-APD based detectors at S  S of PSI: 1.Muon-beam profile measurements (setup of the instruments and beamline optimization); 2.“Large” area detectors (tens cm 2,  ≤ 400 ps) for “standard”  SR spectrometers; 3.Compact fast-timing detectors (  < 100 ps) for the planned 10T instrument. G-APDs: compact, finely segmented, magnetic field insensitive detectors. Restrictions of PMT-based detectors: presence of magnetic fields  light guides  bulky construction: not good for high segmentation; limited time resolution Time-differential  SR correlated detection of individual muons with their decay positrons (muon rates up to 4∙10 4 s -1 ). Time-integral  SR only positron detection at high rate

3. 0 T 1 T 10 x-, 10 y-channels, fibers Ø 1mm, spacing 10 mm Muon Beam Profile Monitor for ALC instrument (28 MeV/c muon beam, up to 5 T field) Muon beam spot size as a function of applied magnetic field 2004

4. Old ALC (PMT-based detector system) New ALC: mounting of the detector module in the solenoid New ALC: detector module (view along muon beam)  New ALC (G-APD based detector)2007

5. New ALC: positron counter EJ-204A (120x28x5 mm 3 ) (120x33x5 mm 3 ) BCF-92 (Ø 1mm)2x SSPM 0701BG Amplifier gain ~20 bw ~ 70 MHz PDE, at 490nm --  30 % Operating voltage --  20 V Gain -- ≤ 4∙10 5 Temp. coeff. of Gain -- < 1.0 %/C Number of micro-cells -- 560 Active area -- Ø1.1 mm SSPM 0701BG Photonique SA 3 mm Detection of mips (U = 42.9V, I 0 = 7.1  A) Amplitude vs. Rate Time resolution ~ 500 mV ~ 150 cells ~ 130 phe

6. New ALC: operation Time-integral (ALC) mode Time-differential mode Muon counter: replaces one of the positron counters in TD-mode Asym = (N bw – N fw ) / (N bw + N fw ) 4-propyl benzoate / methanol (CH 3 OH) Mu addition to ring  2 radicals, not distinguishable in solution

7. “Standard”  SR spectrometer 7T HiTime instrument at TRIUMF (PMT- based detector system) Upper limit for a 10 T spectrometer G-APD based prototype detector PMT based scintillation counters: in high magnetic fields the time resolution is limited due to attenuation and broadening of the light pulses in the necessary light guides. Detection of 1.35 GHz muon spin precession signal in 10T time resolution  ≤ 140ps Per counter (  + / e + ): ≤ 100ps A challenge of muon spin rotation experiments in 10T

8. (1) Positron counter: EJ-232 10x10x5mm; (2) Muon counter: EJ-232 ø8x0.3mm in a 10x10x2mm frame (BC-800); (3) two G-APDs of type MPPC S10362-33-050 (3x3 mm 2, Hamamatsu) PDE > 30% at 390 nm; M ~ 7*10 5 ; U ~ 70 V; 1/M*dM/dT ~ 8% / 0 C (4) scintillator + photosensor in a light tight box; (5) broad band amplifier (gain ~13, bandwidth ~ 600 MHz). Fast timing muon and positron counters (prototypes) Detection of muons (M1) and positrons (P1) in 4.8 T. Test setup: the muon (positron) counters are assembled on a supporting plate inserted into the warm bore of a 5T solenoid. The muon (positron) beam momentum is 28 MeV/c. Time resolution M1-M2 (P1-P2) 46 ps per counter (  + / e + ) P1: Amplitude vs. Rate 2008

9. Summary: We used G-APDs to build several types of detectors for  SR applications. Realization of such detectors with PMTs would have been either more difficult or impossible. This shows a large potential of G-APDs for the development of the  SR experimental technique. 2004 2007  < 50 ps in 4.8 T 2008

10. G-APD + plastic scintillator : time resolution vs. deposited energy (E)(E)  = 19 ps / MeV 0.5 -- best time resolution (NE111 + XP2020UR-M) [M.Moszynski, NIMA 337 (1993) 154] PMT

11. A – MAR—amplifier; CFD – PSI CFD-950; DS0 – LeCroy WavePro 960 (2 GHz ). Scint.: BC422 (3x3x2 mm 3 ) readout via 3x2 mm 2 face G-APDs: MPPC 33-050 (3x3 mm 2, 400 pixels/mm 2 ) MAR-6 amplifier: Gain = 13 (R att = 1k), bw ≈ 600 MHz  (E) : measurement setup

12. Time difference t1 – t2 (A1, A2 in selected windows) Time Resolution of C2 vs. Amplitude (win1 – fixed, win2 – scan)  (E) : raw data Amplitude spectra of C1,C2 Selected amplitude windows

13. 4. Establish the correspondence between N phe and E: N phe = 2270 E n (N phe ) – experimental data (C2, 90 Sr reversed) after the corrections; n (E sim ) – spectrum of deposited energies simulated in GEANT4.  (E) : A  N phe  E 1. Correct for the non-linearity of the amplifier: A  A lin 2. Calculate the number of firing cells: N cell = A lin / A 1c 3. Calculate the number of photoelectrons: N phe = (m / α) ln (1 - N cell / m) m = 2400 (cells per 6 mm 2 ); α = A 1e / A 1c = 1.12 5. σ(A)  σ(N phe ), σ(E)

14. PMT:  = 19 ps / MeV 0.5 best time resolution [M.Moszynski, NIMA 337 (1993) 154]. NE111 (d25 x 10 mm, Teflon reflector) + XP2020UR-M  (E) : results BC422 ≡ NE111 fastest plastic 8400 phe/MeV 370 nm 0.35 / 1.4ns BC422 3x3x2 mm 3, Teflon MPPC 33-050 (3x3 mm 2 ) 70.13 V, 1.0  A Amplifier (2MAR-6) C in = 56pF, R att = 1k BC422 + MPPC 33-050 PDE ≥ 27% 2270 phe/MeV

15. Supporting slides …

16. BC422 3x3x2 mm 3, Teflon MPPC 33-050 (3x3 mm 2 ) 70.13 V, 1.0  A Amplifier (2MAR-6) C in = 56pF, R att = 1k 1e-spectrum C2Averaged waveforms Amplitude spectrum C2 ( 90 Sr – rev.) (trig.=C1, win1 = 0 – ∞)

17.  (E) : GEANT4 simulations Energy losses in C1, C2 Time-of-Flight C1 – C2 (trigger = C2, win2 = 0 – ∞).