Transcript Options for Fiber Based Recoil Electron Detector

Compton Electrons
Dipangkar Dutta & Jeff Martin
Mississippi State & University of Winnipeg
Compton Recoil Electron
Kinematics
• Struck electron loses energy
equivalent to photon energy increase.
Very little angular deflection.
• At 850 MeV, max energy loss is E =
25 MeV [Bates].
• Struck electron is momentum
analyzed using downstream dipole
magnet.
e.g. Mainz Compton
Compton Survey
(focusing on electron detection)
Location
Beam energy
Photon Det.
Electron Det.
Hall A
1.0 – 6.0 GeV
PbWO4
silicon
Mainz
0.1 – 0.9 GeV
NaI
SciFi
SLAC
45.6 GeV
W / quartz
Pb / gas Č
HERA Long.
27.5 GeV
NaBi(WO4)
none
Bates
0.3 – 1.0 GeV
CsI
none
others: NIKHEF, VEPP-3, VEPP-4, SPEAR, CESR, DORIS, PETRA, HERA trans., LEP
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Typical Requirements for
Electron Detector (Mainz & Hall A)
~ 0.5 mm spatial resolution in dispersive direction
high efficiency (no gaps)
high rate capability (up to 100 kHz)
rad hard
Notes:
• Both Mainz & Hall A use CW laser operation (we
don’t intend to)
• background rates highly dependent on energy and
beam tune [Nanda, Hall A]
Rates
Hall-A:
Signal rate : 5KHz for 8mA current @ 500W
(energy independent)
Background : @ 2GeV is 2KHz (depends on beam
tune)
Hall-C:
- Thanks S. Nanda
Laser power is ave. 90W with duty factor of
0.15%
Signal rate: 15-20KHz at 180mA
Background: low (scaled from Hall A rates)
Multiplicity: ~1.5 per pulse
- Thanks Dave
•
Technologies Under Consideration
for
Hall
C
Compton
Silicon
– advantages: proven technology (Hall A), acceptance easy to
understand, rad hard.
– disadvantages: slow? potentially high electronics costs.
• SciFi
– advantages: fast, cheap, use Si-PM readout
– disadvantages: rad hardness? more difficult acceptance?
– alternate: quartz fiber; same readout, very rad hard.
• GEM
– advantages: cheap, rad hard, fairly fast.
– disadvantages: electronics costs hard to estimate, potentially
complicated R&D project on its own.
Si cost estimate (C. Davis, et al 2005
NSERC submission)
Item
Cost (kCAD)
Si detectors (8 x PIPS-S-8)
44
Electronics @ 192 channels
82
Cooling
8
Misc
2
Travel
10
Total
146
Note: RTI category 1 limit is $150 kCAD.
Options for Fiber Based
Recoil Electron Detector
 Scintillating Fiber Based Device
(SciFi, e.g. Mainz Compton)
 Quartz Fiber Based Device
(e.g. SLAC Compton -photon detector, 25m resolution)
SciFi Based Electron Detector
SciFi available from 3 manufacturers
Bicron, Kuraray & Pol.Hi.Tech.
Typical light yield 4.5 p.e./mm, for
1mm diameter fiber. Achieved
resolutions of ~125mm.
Kararay is the most radiation hard
no damage detected when exposed
to 1Mrad (tested with e- beams).
E. C. Aschenauer et al. hep-ex/9710001
“We have not found any noticeable change in the detector properties
over time.”
-Yoshio Imai (Mainz Compton)
Quartz Fiber Based Detector
Signal through Cerenkov radiation,
thus low photon yield (only few% of
photons is trapped) ~1 pe/GeV/cm.
Also incidence angle dependent.
But 25mm resolution achieved at
SLAC, extremely radiation hard
~ 2 Grad, insensitive to soft
synchrotron radiation and high
linearity.
Light Detection
Mainz used Multi Anode PMTs made by Hamamatsu
SiPM:
the new kid on the block
Silicon Photo Multipliers - densely packed array of Avalanche Photo
Diodes (~1000 in a 1mmx1mm grid) operating in Geiger mode
(i.e. individual photo-electrons from each micro pixel cannot be
distinguished).
~ 1 mm
20~100 mm
400 pixels
~ 8 mm
Depletion
region
~ 2 mm
Substrate
First developed and produced by
CPTA Russia. Now also
Hamamatsu Photonics
Performance
PMT
SiPM
Gain
~106
105~106
Photon Detection
Efficiency
0.1 ~ 0.2
0.1~ 0.4
Response
fast
fast
Photon counting
Yes
Great
Bias voltage
~ 1000 V
30 ~ 70 V
Size
Small
Compact
B field
Sensitive
No influence
Cost
Not low
Low (~$10)
Dynamic range
Good
Not so good
Stability
Good
Unknown, maybe good
Noise (fake signal
by thermions)
Quiet
Noisy (order of MHz)
can reduce by cooling
Roadmap to First Light
• Decide technology ASAP
– Base decision on:
• rates (signal and background)
• granularity (guess similar to Hall A and Mainz?)
• fiducializability?
– Current favorite: …? Input from collaboration/experts?
• Begin detailed budgeting for upcoming grant cycles
– NSERC: deadline end of Oct.
– DOE: deadline Nov.
– Need ideas on how to split tasks (MSU vs. UWpg/Canadians)
• Detailed simulations – decide position wrt chicane dipoles.
• Prototyping
• Receive funding
• Build it