Position Sensitive SiPMs for Ring Imaging Cherenkov Counters C.Woody BNL January 17, 2012.
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Transcript of Position Sensitive SiPMs for Ring Imaging Cherenkov Counters C.Woody BNL January 17, 2012.
Position Sensitive SiPMs for Ring Imaging Cherenkov
Counters
C.Woody
BNL
January 17, 2012
C.Woody, SiPMs for RICH, 1/17/12 2
Cherenkov Radiation
nc
1cos
Light emitted as a “shock wave” when a charged particle travels faster than the speed of light in a dielectric medium
kp
v
p
cn
v
v =c = particle velocity
= group velocity of photon
= refractive index
dk
dn
n
ck
n
c
dk
dg
2
v
= phase velocity of photon
Dispersion
cn
c v
For Cherenkov radiation to be producedtn
ctg v
n
cp v
Threshold velocity:nc
1
Symmetric in Light is emitted in a cone
from a line source
p
• L.M.Frank and Ig.Tamm C.R.Acad.Sci. USSR, 14 No.3 (1937) 109-114• Ig. Tamm, J.Phys. USSR 1 (1939) 439• J.V. Jelly, Cherenkov Radiation and it Applications (1958)
C.Woody, SiPMs for RICH, 1/17/12 33
Cherenkov Spectrum
22
21
sin2
cdxd
Nd
Spectrum peaks in the deep (V)UV
12
22
11sin2
cddxd
Nd
dx
dN
Differential Spectrum:
Integral Spectrum
2
22 11cos1sin
ncc
Note: Spectrum is UV divergentHowever, in real materials, n is dispersive and < 1 at short wavelength
Self absorption limits intensity at short wavelengths
Where 1 and 2 are the wavelengths of transmission of the radiator material
137
12
c
e
C.Woody, SiPMs for RICH, 1/17/12 44
Cherenkov Detectors
2
2 )(sin)(2 d
LN cpe
dEEeVcmd
cmN )()(370)(2)( 112
10
cpe NLN 20 sin
peWMR PDETRT )()()()()(
Figure of Merit :
Two types of detectors• Threshold Detects only the presence of light emitted by a particle with a velocity greater than c
• Ring imaging Measures the ring produced by the light emitted into the Cherenkov cone Can use a spherical mirror to focus the light from the line source into a ring
Detection efficiency depends on: • length of radiator• transmission of radiator • reflectivity of mirror (if any)• transmission of window (if any)• photon detection efficiency of photodetector• photoelectron detection efficiency
2
2
)(
11)(sin
nc
C.Woody, SiPMs for RICH, 1/17/12 55
Threshold Cherenkovs
Air Aerogel Water Quartz PbGl PbF2
Density (g/cm3) 1.2x10-3 0.2-0.4 1.00 2.2 6.3 7.77Index of refraction 1.0003 1.01-1.10 1.33 1.46 1.8 1.78
Radiation Length (cm) 3.1x104 68-136 36 12.3 1.26 0.93Npe/cm for N0=100 0.06 9 43 53 69 68
Typically want to identify/separate /K/p’s over some momentum range
For a given radiator, each particle will have a different threshold momentum for producing Cherenkov light
For particle id, p=mv = m0
e.g., for air, n=1.0003, c = 1/n = 0.9997, c=40.8
21
1
Particle m0 (MeV) pthresh (GeV) 140 5.7K 494 20.2p 938 38.3
Threshold counting:
Typically use two threshold counters with two different radiators for /K/p separation over some momentum range
C.Woody, SiPMs for RICH, 1/17/12 66
Ring Imaging Cherenkovs (RICHs)Measure the diameter of the ring produced by the cone of Cherenkov light
Two ways of focusing the light into a ring:
Proximity focused Mirror focusedDIRC
Combined
Uses trapped light (internally reflected) from proximity focused type radiator to form ring imageSpherical mirror with detector
plane at the focal distance RM/2
Radiator
Window
WindowExpansion
medium
Detector
Detector
p
C.Woody, SiPMs for RICH, 1/17/12 77
PHENIX RICH
Ring Imaging Cherenkov counter with large mirrorsand PMT readout
• 5120 1-1/8” PMTs equipped with Winston Cones• Gas radiator (ethane)• Pion threshold = 3.7 GeV/c, ~ 20 /ring• Ring resolution ~ 1° in and (R ~ 14.5 cm for ) • t < 1 ns
C.Woody, SiPMs for RICH, 1/17/12 8
Particle ID with RICHsMeasure the particle velocity and momentum independently determine particle’s mass
Figure of merit for a RICH detector:
pe
rNLN
nk
tan
0
• T.Ypsilantis & J.Seguinot, NIM A343 (1994) 30-51 Theory of Ring Imaging Cherenkov Counters• B. Ratcliff, NIM A502 (2003) 211-221 Imaging Rings in Ring Imaging Cherenkov Counters
rkp
mmn
2
21
22
2
||
For two particles of mass m1 and m2 with momentum p well above threshold (~1), their separation n is given by:
BaBar DIRC (Radiator = quartz)
= total angular error per detected photon
C.Woody, SiPMs for RICH, 1/17/12 9
HERMES Dual Radiator RICH PMTs = 0.75” with Winston Cones
Aerogel C4F10
Angular Resolution
~ 7.6 mrad ~ 7.5 mrad
N.Akopov et.al., Nucl. Inst. Meth. A479 (2002) 511-530
C.Woody, SiPMs for RICH, 1/17/12 10
Photon Detection Efficiency with PMTs
HERMES RICH
Aerogel
C4F10
C.Woody, SiPMs for RICH, 1/17/12 1111
Detection of Internally Reflected Cherenkov LightDIRC
Concept: Use Cherenkov radiator (quartz bar) to propagate internally reflected light to an image plane at the end of the radiator
Use external tracking detectors to measure entry location and direction of incoming track Also to measure momentum and time
Functions as an imaging detector - rectangular bar preserves angle information (c ,c) - ring is imaged onto xy (r) plane of PMTs - measuring arrival time of photons gives 3rd z coordinate
Must worry about chromatic dispersion I.Adam et.al., Nucl. Inst. Meth. A538 (2005) 281-357B.Ratcliff, Nucl. Inst. Meth. A502 (2003) 211-221
z
gp ck
Lnt ng()=n()-dn()/d Group Velocity
kz = direction cosine in z-directionBaBar Experiment at SLAC
C.Woody, SiPMs for RICH, 1/17/12 1212
BaBar DIRC
<n1> = 1.473 (quartz)
Bars need to be square(< 0.25 mrad) and smooth (roughness < 7.5Å)
n3 = 1.0 (N2)
n2= 1.346 (water)
Used to minimize internal reflection at quartz-water interface
Performance:
N0 = 25 cm-1
<Npe> = 23 for =1 particle
1-1/8” PMTs
C.Woody, SiPMs for RICH, 1/17/12 13
BaBar DIRC Angular Resolution
=2.5 mraddet22
)(2 coln
• n() = chromatic dispersion• col = distortions due to light collection• det = detector resolution
Overall track resolution:
1-1/8” PMT @ 1.17m ~ 7 mrad (single )
Assuming 23 p.e per ring ~ 1.5 mrad
XY
Z
HERMES RICH(single photon)
Consider contribution to detector resolution:
C.Woody, SiPMs for RICH, 1/17/12 14
Photon Detection Efficiency with SiPMs
Consider the Hamamatsu S11064-050P
4x4 array of 3x3 mm2 SiPMs50 m pixels, 3600 pixels per SiPM61.5% fill factorDark counts per channel (> 0.5 pe) - 6 MHz
1110 277)(370 cmdEEeVcmN
~ 0.75 eV
E = 4.13 eV (300 nm) 1.38 eV (900 nm) = 2.75 eV
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Photon Energy (eV)
PD
E*d
E
PDE dE
C.Woody, SiPMs for RICH, 1/17/12 15
SiPM Angular Resolution
Assume can locate the photon to 25 m
x = y = 25 m/12 = 7.2 m
To achieve the same angular resolution as BaBar, one could reduce the expansion length by a factor of 25 mm/25m = 1000 !
Could also greatly reduce area coverage:
Cross section of a BaBar radiator bar = 1.75 x 3.5 cm = 6 cm2
could cover entire end of bar with ~ 65 3x3 mm2 devices
C.Woody, SiPMs for RICH, 1/17/12 16
MPPC Readout of Cherenkov Light
E.Garutti, SiPM Workshop, CERN
C.Woody, SiPMs for RICH, 1/17/12 17
Trig
Trig
Readout
ReadoutBit Register
Bit Register
Latch
LatchSPAD Disc
0 0
0 01
0 01
0
0
0
0
11
Possible way to save and readout hit SPAD address
C.Woody, SiPMs for RICH, 1/17/12 18
Noise~ 1 MHz = 1 sec
Trig (~ 1 ns)
C.Woody, SiPMs for RICH, 1/17/12 19
SiPM Readout Chips
C.Woody, SiPMs for RICH, 1/17/12 20
Summary and Challenges
• Possibility to detect single photons with a spatial resolution ~ 25-50 m (this may be a first… and could possibly have many other applications)• Could potentially greatly improve the angular resolution for a RICH/DIRC ( improved )• Could greatly reduced expansion volume for a RICH or DIRC (requires only modest area coverage)• Can provide fast timing (needed for DIRC or TOF RICH)
• Need to integrate first level readout electronics onto the SPADs• Must detect single photoelectrons in the midst of very high noise • Device must be triggerable
C.Woody, SiPMs for RICH, 1/17/12 21
Backup Slides
C.Woody, SiPMs for RICH, 1/17/12 22
5 - 91 - 5 n=1.007
th~8.5
Aerogel
17 -5 - 17 n=1.00044
th~34
RICH
0 - 50 - 2.5 ~100 psTOF
Kaon-Protonseparation
Pion-Kaonseparation
0 4 8
0 4 8
0 4 8 0 4 8
0 4 8
0 4 8
Combined Particle ID Using Threshold Cherenkov, RICH and Time of Flight
(PHENIX)
C.Woody, SiPMs for RICH, 1/17/12 2323
PHENIX Time of Flight Counter
1000 finely segmented slats Read out on both ends with 2000 PMTs
t < 96 ps (used with fast “Beam-Beam” counter to define start time)
K/ separation to ~ 2 GeVcp/K separation to ~ 4 GeV/c
ScintillatorBasePMT-metal
Light Guide/miror