TEVATRON IONIZATION PROFILE MONITOR

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TEVATRON IONIZATION PROFILE MONITOR

• Andreas Jansson
• Fermilab

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People

• AD
• C. Rivetta
• L. Valerio
• J. Zagel
• B. Dysert

• CD
• M. Bowden
• R. Kwarciany

• PD
• Bross
• K. Bowie
• H. Nguyen
• T. Fitzpatrick

Also help from D. Harding (TD), V. Kashikin
(TD), T. Zimmerman (PD), Z. Tang (PD) and the Tev
Techs
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Talk outline

• Motivation for IPMs
• Challenges in Tevatron
• Design of Tevatron IPMs
• Tests
• Pictures from the tunnel

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Motivation
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IPM working principle

• Measure distribution of rest gas ionization by
• Drifting ions onto a detector using an electric
  field, or
• Drifting ionization electrons onto a detector
  using a EB field.

Beam
-
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Challenge I Small beam size

• Small beam size
• Low gas pressure

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Challenge II Beam separation
Y mm
Inj. old helix
Inj. new helix
Flattop
X mm
? 20 ? mm mrad ?p/p 7.5 10-4
One and three sigma contours
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Challenge III Residual gas pressure

• Gas pressure at E0 before 2004 shutdown was in
  low 10-8s, slated to be improved
• Based on estimated gas composition, expect about
  1000e/bunch for a ¼ mm ?10 cm detector at 3 108
  torr and 2.7 1011 protons/bunch.
• Need for a local vacuum bump after vacuum
  inprovements.

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Challenge IV Parasitic signals
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Simulations

• Injection is most difficult (fewer counts per
  channel).
• Signal per bunch is small, but gain limited by
  MCP saturation effects from total (proton)
  signal.
• Need about 300 primaries (per bunch) for 10
  beam width accuracy (requires gas injection).
• Higher accuracy can be obtained by averaging many
  turns (ramp measurement).

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Fermilab QIE8 ASIC

• Charge Integrating Encoder (QIE)
• Developed at Fermilab
• Used by KTeV, CDF, Minos, CMS
• Frequency range 7-53 MHz
• No deadtime.
• LSB 2.6fC in logarithmic mode, 0.9fC in linear
  mode
• Dynamic range gt104 in logarithmic mode
• Can achieve noise of O(1fC)

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MCP test stand
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MCP saturation
Turn
Measured emittance vs MCP voltage in MI IPM at
different points in the acceleration cycle

• MCP output current per unit area is limited by
  MCP pore recharge time.
• Onset of saturation observed in MI IPMs, as
  expected from calculations.
• Will abandon Chevron configuration since extra
  gain can not be utilized (allows to run at higher
  bias).

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QIE test stand

• Using laser based PMT test setup in Lab6
• KTeV test board modified with CMS-QIE
• Observed good linearity and insensitivity to
  clock phase

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Tracking transverse displacement
B0.2 T, E100kV/m
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Cable tests

• Stepping QIE clock phase w.r.t the incoming
  pulse, can improve time resolution
• Derivation of composite signal yields the
  original pulse
• Used to study reflections due to connectors in
  front-end cabling

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Rad level measurements

• Reading 125 mrad/h during normal running at 4.5
  feet
• 18 years to 20 krad!

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Component rad tests

• Tested commercial TI serializer in Tevatron
  tunnel for gt200 days.
• Previously tested (by others) for total dose
  Mrad.
• Only handful of link errors seen.
• One latchup candidate, cleared by cycling power.
• Observed error rate should not affect operation.

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Detector design

• Based on MI eIPM prototype
• Flange-mounted detector for quick installation
• Many modifications
• Better screening
• Provisions for calibration device

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Anode board
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Magnets

• Single corrector for simplicity.
• Electromagnets chosen.
• Can be turned off to verify effect on measurement
  and machine.
• Bought from outside manufacturer.

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Field quality

• E-field is not perfect longitudinally
• EB component produces a small transverse drift
  velocity
• To first order, this generates a rotation of the
  beam image, removed by beam-based alignment
• Higher order terms distort the beam image, expect
  order 30 nm rms effect on beam size.

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DAQ system

• CMS-QIE front end in tunnel.
• Serial data uplink on optical fiber
• Receiver and data buffer in upstairs PC
• Timing clock QIE settings supplied from PC
  thru cat-5E cable

Host PC (LabView)
Data Buffer (PCI)
Timing card (PCI)
Timing fanout
QIE cards (16x 8 ch)
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Timing card

• Produces the 15MHz (2/7 RF) FE clock
• Decodes and transmits beamsync clock (p pbar)
  injection events
• Transmits QIE settings
• Separate version of card will decode TCLK/MDAT

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Timing scheme
396 ns (21 buckets)
p/pbar separation
RF
2/7
1/7
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Front end card

• 8 channels (CMS QIE) per board.
• Data is serialized by CERN GOL ASIC (rad hard)
  and sent thru fiber
• Timing fanout board cleans up and distributes
  clock and timing signals

QIE card
timing fanout
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Data buffer card

• Doubles as BTeV L1 data buffer prototype.

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Controlled N2 leak system
Leak 1
Ion pump
Leak 2
Isolation valve
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Differential pumping scheme
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Controlled N2 leak tests at E4R
leak on
Red traces IP and IG in leak chamber Green, Blue
and Cyan IPs and IG in main chamber
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Tunnel installation
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Conclusions and outlook