Fast Timing Cerenkov Detector

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Fast Timing Cerenkov Detector

• A. Bross, R. Dysert
• Fermilab
• X. Yang
• UCLA
• V. Rykalin
• NIU/NICADD

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MuCool
Measure 6 dimensional phase space of 150-300
MeV/c muon beam before and after cooling. x x
y y - TPCs p - bent solenoid t - determine
momentum kick from RF cavity 805 MHz (10 ps)
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Then came a Minimalist Approach to MUCOOL Þ MICE
Cooling Channel
Beam
TPC
TOF
PID
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Fast Timing Cerenkov Detector (FTCD)

• Technical concept of Fast Timing Cerenkov
  Detector
• Direct image MgF2 Cerenkov disk using CsI PC
• Electron multiplier - micro-channel plate (MCP)
• 50 W High frequency anode/connectors/cabling

Basic Structure UHV enclosure Cerenkov
radiator 2-5 mm MgF2 CsI Photocathode MCP
stack 50 Ohm anode
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MCP TOF Detector for IonsKraus et.el, NIM A264
(1988) 327

• Large-Area Fast-Timing Detector
• 50 ps
• Ions
• 25 and 40 mm Æ

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Fast Timing - Cerenkov Detector

• Thin MgF2 radiator (Head-on as viewed by beam)
• CsI Photocathode

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FTCD

• Wavelength region 120 - 200 nm
• Cosqc 1/bn
• For 5 mm radiator Þ dt 3 ps ( not weighted for
  dng/dn)
• For CsI PC expect 70 pe

Anderson, Kwan, Peskov - Solid CsI PC Lu,
McDonald Semi-Transparent PC
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Cerenkov Radiator Semitransparent CsI
Photocathode

• MgF2 (Polished Magnesium Fluoride Substrate) from
  Bicron (25mm thick Ø 25, 33, 50mm)

d
MgF2
Cr (metal film)
MgF2
MCP
/
MSP
CsI
photoelectrons
anode
photoelectrons
Al ring
FNAL LAB7 Facility (Vacuum Deposition/Thin Film
Coatings ) 1. Cr film and Al ring sputtering on
substrate 2. Re-furbishing CsI evaporation
setup
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Test of Cerenkov Radiators CsI photocathode
(LAB6 facility)
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Chambers for CsI efficiency measurements
C.Lu, K.T.McDonald, NIM A343 (1994)
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CsI (100A) efficiency Hamamatsu PMT vs. FNAL
photocathode
1. Hamamatsu PMT R6835 (work as a diode,
Gain1) 2. Chamber with a)input window 2mm
Bicron MgF2 (Cr) b) photocathode 100A
CsI (FNAL)
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FTCD

• Very High gains possible
• Z-Stack
• G 2 X 108

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Galileo Time-of-Flight Detector

• Fabricate mosaic (5 X 5 area, 18 mm pixels) based
  on existing product

Gain 1 X 107
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MCP Magnetic Field EffectG.W.Fraser, NIM A291
(1990)
Magnet field effect

Field aligned with MCP channel
u
axis.
Electrons are bent in field,
s
mean-free path between wall
interactions - smaller (less
acceleration/less gain), but
more interactions/unit path
length along channel

Non linearity
Higher Electrostatic
u
(accelerating) field gives
smaller effect
Smaller channel pore gives
u
smaller effect
Currently, smallest pore is 2
s
micron
Variation of single-MCP gain with bias voltage,
channel diam. And axial magnetic field strength.
L/D801. Curve (a)-(f) represent gain
calculated at 100V intervals over range 800V(a)
to 1300V(f) full curves stand for D2mm, broken
curves for D6mm, and dotted curves for D12,5mm.
New Devices
s

MCP with
submicron
pore

Micro-Sphere-Plates
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Mechanical Design
Modular design makes it simple to interchange
parts to study different configurations.
to pump
UHV enclosure
MCP HV feed through connector
MgF2 Substrate(changeable) (as a Cerenkov
radiator) CsI photocatode
Anode 25GHz connector
Input window (quartz)
MCP stack (changeable) (chevron or Z)
PC HV feed through connector
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Mechanical Design
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Detector assembly
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Mechanical Design
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Mechanical Design
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FTCD Test Setup

• Two head operation
• Vacuum system
• Turbo pump
• P 5 X 10-9
• High Voltage
• Max potential in system lt 5KV

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MCP Pulse Out

• Typical pulse response for single pe initiated
  avalanche in MCP
• G ³ 107
• tr 200 ps
• Some reflections
• Anode Structure
• Protection circuit at DSO

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MCP Chevron Pulse Ht. Dist

• Chevron config. Using Hamamatsu MCP
• MgF2 radiator with CsI PC
• Data with Xe UV pulser (193 nm)
• G 2 X 107
• 1 and 2 pe clearly visible

First pe
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Timing DAQ

• Currently using DSO
• Tek 10 Gs/sec scope
• 4 channel
• Have used to measure speed of light
• Roughly 3 ps (RMS) in averaging mode
• Working with HYPRES
• Superconducting TDC
• 20 GHz clock with 16 stage interpolator
• 3-5 ps time bin
• First examples not ready until summer

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Performance of First MCP Detector

• Full Detector
• ChevronMgF2CsI
• Excited with Xenon pulser
• m 1 pe
• Measured Fall time and jitter _at_ 1 pe
• 10 40 mV
• 100 trigger average
• lttfgt 170 ps
• st 6.5 ps!

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Cosmic-Ray Data

• We have run two-head system with cosmic-ray
  trigger
• Unfortunately signal from PC is very small for
  mips
• Unable to do timing measurement using cosmics
• Implies very low QE
• Photocathode(s) were measured to be good
• Degradation in handling?
• Degradation during repeated bake-out cycles
• We experienced vacuum problems
• Currently in processing of producing new CsI PCs
• Should be ready to test next week

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FTCD-Superconducting TDC

• Electronics
• Hypres
• Demonstrated 32 GHz SC-TDC
• Proposing 20 GHz counter with analog interpolator
• 3-5 ps lc
• Work currently being done on DOE SBIR
• Two channel SC TDC with interpolator chip in
  processing

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SC TDC Cryo

• Simple flow cryostat system from Oxford
• 2 L/hr LHe usage
• If background low Hypres prototype system
  sufficient
• Will depend on required number of channels
• Hypres estimates delivery of first TDCs late
  spring

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SC TDC Cryo

• Two channel cryo-probe detail

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Conclusions

• Initial tests indicate timing with 10 ps
  resolution is possible with this technology
• st lt 10 ps for 1 pe
• We need to improve our CsI photocathodes
• 20 QE in relevant spectral range should be
  possible based on published data/procedures
• Should give mip signal of 50-70 pe for 5 mm MgF2
• Near-term plan
• Study Galileo/Burle, Hamamatsu MCPs
• Two head system with cosmic-ray trigger, DSO DAQ
• Install Hypres SC TDC
• Beam Test this summer
• Study magnetic field effects at Lab G