UIC Physics Department

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UIC PhysicsDepartment

• Fast Timer Project

Bob Dysert, Alan Bross - Fermilab
November 18, 2005
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MICE

• Simple in theory

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MICE

• Muon cooling is needed to fit a beam into
  accelerator
• Need fast timing measurement to tag muons in RF
  bucket for acceleration
• Initial design RF805MHz required 10ps
  resolution
• Revised design RF201MHz requires only 50ps
  resolution

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Fast Timer Operation
f Fermilab

• Particles pass through radiator (MgF2)
• Cerenkov light converted to electrons in
  photocathode (CsI)
• Electrons hit high gain MCPs
• Output of MCPs is collected on 50? anode
• Anode output is read out on fast oscilloscope or
  superconducting TDC
• TDC operation requires two detectors one start,
  one stop

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Fast Timer Readout

• Digital Tektronics oscilloscope 10GS/s, 3GHz,
  4-Ch
• Superconducting TDC with 3-5ps per bin (never
  received)

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Hardware Setup
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UHV Enclosure
MgF2 Radiator
50? Anode
SMA Feedthrough
Particles
MCP Stack
CsI Photocathode
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System Potentials
MCP Out -1kV
FlangeGND
Anode -100V
MCP In -3.1kV
PC -4.1kV
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MCP Performance
G 2E8 w/ Z-stack
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Mechanical Setup
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MgF2 Window
Spring Loaded Top Plate
HV Feedthrough
HV Wings
MCPs
Ceramic Spacers
Baseplate
Anode
Threaded Rod
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Mechanical Setup - Baseplate
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Mechanical Setup - Baseplate
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Mechanical Setup - Anode
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Mechanical Setup - Anode
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Mechanical Setup MCPs
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Mechanical Setup Photocathode
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Mechanical Setup Complete
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Vacuum System
Cold Cathode Gauge
Gate Valve
Leybold TMP50
Vacuum Can
Heat Tape
Roughing Pump
Ceramic Isolation
Quartz Window
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Vacuum System
PMTs
Detector HV Cables
Xenon Pulser
Scintillator Paddles
Bleed-up Valve
Heating Tapes
Cold Cathode Readout
APD for Trigger
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Problems

• Poor vacuum
• Source Quartz window leak
• Source MCPs outgassing
• Source Gas trapped?
• Souce Dirty components
• Solutions Plug leak, Bake out, Score screws, and
  clean.

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Problems

• Arcing w/o MCPs in stack
• Source Wings arc to grounded threaded rod
• Solution PC potential rod potential
• Arcing w/o MCPs in stack
• Source Threaded rod arcing to grounded vacuum
  flange
• Solution Solder threaded rod/nuts to prevent
  movement and eliminate sharp edges

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Problems Contd

• Breakdown w/ MCPs
• Source Resistance mismatch between MCPs in stack
• Solution Match MCPs
• No apparent signal
• Source Photocathode had degraded
• Solution Transport and assemble only in N2
  environment

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Signals
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Signals
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Signals
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Signals
Data from Xe UV Pulser (193 nm) G 2E7 1st and
2nd PE clearly visible
1st PE
2nd PE
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Questions?
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bross_at_fnal.gov rdysert_at_fnal.gov
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TDC Channel
2ps resolution with analog prescale
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Fast Timing - Cerenkov Detector

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

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Fast Timing Cerenkov Detector

• 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