1
Application of G-APDs in
Muon Spin Spectroscopy
2
G-APD + plastic scintillator:
some results on the time resolution
A. Stoykov, R. Scheuermann, K. Sedlak
NMI3 – Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy,
Joint Research Activity (JRA8): MUON-S. Contract: RII3-CT-2003-505925
GSI 9Feb09
G-APDs in SR
Time-differential SR
correlated detection of individual muons with
their decay positrons (muon rates up to 4∙104 s -1).
Time-integral SR
only positron detection at high rate
Restrictions of PMT-based detectors:
presence of magnetic fields  light guides 
•
bulky construction: not good for high segmentation;
•
limited time resolution
G-APDs: compact, finely segmented, magnetic field insensitive detectors.
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 cm2,  ≤ 400 ps) for “standard” SR spectrometers;
3. Compact fast-timing detectors ( < 100 ps) for the planned 10T instrument.
Muon Beam Profile Monitor
for ALC instrument (28 MeV/c muon beam, up to 5 T field)
2004
10 x-, 10 y-channels,
fibers Ø 1mm, spacing 10 mm
2.0
x
y
 (cm)
1.5
1.0
0.5
no collimators,
beam window 70 mm diam.
0.0
0
1
2
3
4
H (T)
0T
1T
Muon beam spot size as a function
of applied magnetic field
5
Old ALC (PMT-based detector system)
New ALC (G-APD based detector)
New ALC: mounting of the detector module in the solenoid

New ALC: detector module (view along muon beam)
2007
New ALC: positron counter
SSPM 0701BG
EJ-204A (120x28x5 mm3)
(120x33x5 mm3)
BCF-92 (Ø 1mm)
PDE, at 490nm
Operating voltage
Gain
Temp. coeff. of Gain
Number of micro-cells
Active area
Detection of mips
(U = 42.9V, I0 = 7.1A)
2x SSPM
0701BG
Amplifier
gain ~20
bw ~ 70 MHz
Photonique SA
-------
 30 %
 20 V
≤ 4∙105
< 1.0 %/C 3 mm
560
Ø1.1 mm
Amplitude vs. Rate
A / Amax
1.0
~ 500 mV
~ 150 cells
~ 130 phe
0.5
F13: U = 42.9V, I0 = 7.1A
0.0
3
10
Counts
12 ~ 450ps
1 ~ 320ps
100
0
-3
-2
-1
0
t (ns)
1
2
5
10
-1
Count rate ( s )
Time resolution
200
4
10
3
6
10
New ALC: operation
Time-differential mode
Time-integral (ALC) mode
0.8
5
0.7
Ag, zero field
10
0.000
-0.004
0.6
Counts
Asymmetry
4
10
-0.008
sp658
-0.012
1.90
1.95
2.00
2.05
2.10
2.15
0.5
0.4
4PBA/MeOH, RT
sp652 :
0 - 4.50 T,  = 0.050 T
sp658 : 1.90 - 2.15 T,  = 0.001 T
0.3
0
1
2
3
Asym = (Nbw – Nfw) / (Nbw + Nfw)
COO-
C3H7
-4
2
10
Bg
Bg / N0 = 2*10
1
10
B (Tesla)
N0 exp( t / )
3
10
0
5
10
Time (s)
15
20
Muon counter:
replaces one of the positron
counters in TD-mode
4-propyl benzoate / methanol (CH3OH)
Mu addition to ring  2 radicals,
not distinguishable in solution
A challenge of muon spin rotation experiments in 10T
Detection of 1.35 GHz muon spin precession signal in 10T
 ≤ 140ps
Measured asymmetry (% of max.)
Muon-spin precession frequency (GHz)
0.0
0.4
0.8
Per counter ( + / e+ ): ≤ 100ps
1.2
100
time resolution
 = 65ps
G-APD based prototype detector
80
140
60
Upper limit for a 10 T spectrometer
50
40
170
7T HiTime instrument at TRIUMF
(PMT- based detector system)
400
“Standard” SR spectrometer
20
0
0
2
4
6
8
10
Magnetic field (Tesla)
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.
Fast timing muon and positron counters (prototypes)
H (0 -- 4.8 T)
2008
 + (e+ )
25
M1 (P1)
M2 (P2)
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.
(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 mm2, Hamamatsu)
PDE > 30% at 390 nm; M ~ 7*105; U ~ 70 V; 1/M*dM/dT ~ 8% / 0C
(4) scintillator + photosensor in a light tight box;
(5) broad band amplifier (gain ~13, bandwidth ~ 600 MHz).
Time resolution M1-M2 (P1-P2)
400
H = 4.8T
P1: Amplitude vs. Rate
1.0
200
0.8
 = 60 ps
0
A / Amax
Counts
M1 -- M2
200
P1 -- P2
0.6
0.4
Detection of muons (M1)
and positrons (P1) in 4.8 T.
0.2
 = 65 ps
0
-0.2
0.0
0.2
t (ns)
46 ps per counter (  + / e + )
0.0
0.01
0.1
1
Count rate (MHz)
10
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.
2007
2004
 < 50 ps in 4.8 T
2008
(E)
G-APD + plastic scintillator :
time resolution vs. deposited energy
PMT
 = 19 ps / MeV0.5
-- best time resolution (NE111 + XP2020UR-M)
[M.Moszynski, NIMA 337 (1993) 154]
(E) : measurement setup
Scint.: BC422 (3x3x2 mm3) readout via 3x2 mm2 face
G-APDs: MPPC 33-050 (3x3 mm2, 400 pixels/mm2)
A
– MAR—amplifier;
CFD – PSI CFD-950;
DS0 – LeCroy WavePro 960 (2 GHz ).
Aout (mV)
2MAR-6 linearity
(Ratt = 1k)
1200
800
400
Aout = A max*(1 - exp (-k Ain / Amax ))
Amax = 4757 mV, k = 13.2
0
0
MAR-6 amplifier: Gain = 13 (Ratt = 1k) , bw ≈ 600 MHz
20
40
60
80
Ain (mV)
(E) : raw data
Counts (normalized)
1.0
Amplitude spectra of C1,C2
Selected amplitude windows
C1
0.5
ampl. window
(fixed)
1.0
C2
0.5
ampl. window
(scan)
0.0
0
50
Time difference t1 – t2
(A1, A2 in selected windows)
200
12 = 41 ps
0
-0.1
A (pC)
140
120
100
80
1 = 29 ps
-0.2
150
Time Resolution of C2 vs. Amplitude
(win1 – fixed, win2 – scan)
0.0
0.1
0.2
 (ps)
Counts
400
100
60
40
t (ns)
20
6
8
10
20
A (pC)
40
60
80
(E) : A  Nphe  E
A  Alin
1. Correct for the non-linearity of the amplifier:
2. Calculate the number of firing cells: Ncell = Alin / A1c
3. Calculate the number of photoelectrons: Nphe = (m / α) ln (1 - Ncell / m)
m = 2400 (cells per 6 mm2); α = A1e / A1c = 1.12
4. Establish the correspondence between Nphe and E:
Nphe = 2270 E
n (Nphe ) – experimental data (C2, 90Sr reversed) after the corrections;
n (Esim ) – spectrum of deposited energies simulated in GEANT4.
0
Counts (norm.)
1.0
500
750
1000
1500
C2
90
Sr -- rev.
Nphe
Nphe
Esim
0.5
5. σ(A)  σ(Nphe), σ(E)
0.0
0.0
0.2
0.33 0.4
0.6
Esim (MeV)
(E) : results
BC422 + MPPC 33-050
200
400
600
800
Nphe
140
120
2270 phe/MeV
PDE ≥ 27%
100
80
 (ps)
BC422
60
3x3x2 mm3, Teflon
MPPC 33-050 (3x3 mm2 )
40
 = 18 ps / E
20
0.02
70.13 V, 1.0 A
0.5
Amplifier (2MAR-6)
Cin = 56pF, Ratt = 1k
0.04
0.06 0.08 0.1
0.2
0.4
E (MeV)
PMT:  = 19 ps / MeV 0.5
best time resolution [M.Moszynski, NIMA 337 (1993) 154].
NE111 (d25 x 10 mm, Teflon reflector) + XP2020UR-M
BC422 ≡ NE111
fastest plastic
8400 phe/MeV
370 nm
0.35 / 1.4ns