Antiproton Source

1
Antiproton Source

• Keith Gollwitzer
• DOE Tevatron Operations Review
• March 27, 2007

2
Outline

• A typical day of Operations
• Overview
• Improvements done during the last year
• Stacking Cooling Team
• Performance

3
A Good Day of Stacking

• Stack Cycle is 2.4s
• Stacking cycle is
• 2-3hr (40-50mA)
• Pbar transfers (non-stacking) time is lt15min
• Leave behind lt8mA
• Other Main Injector cycles that support fixed
  target, studies and filling the Tevatron reduce
  the stacking rate

4
Quick Overview - Production

• Two Booster batches are slip-stacked in Main
  Injector before batches destined for NUMI
• 120GeV proton beam is extracted from Main
  Injector (7-9 e12)
• 120GeV beam line brings beam to target
• Downstream of target is Collection Lithium Lens
  followed by Pulsed Magnet which focuses and
  steers secondaries into AP2 beam line
• AP2 Beam line transports large secondary beam to
  Debuncher

5
Quick Overview - Debuncher

• Arriving Secondaries are ?p/p 2.25
• Pions and muons decay within 30 turns
• Electrons do not survive first turn
• Designed admittance is 35? mm-mrad
• Accepts beam of gt 330? mm-mrad beam emittance
• Bunch Rotation in 50 turns reduces the momentum
  spread
• Phase Space reduction in 2 seconds
• Stochastic Cooling
• 4-8 GHz of Bandwidth
• 8 Narrowband Pickup channels
• 4 Narrowband Kicker Channels
• Factor of 10 in longitudinal phase space
• Factor of 7-10 in both transverse phase space
  dimensions
• Transfer to Accumulator

6
Quick Overview - Accumulator

• RF system decelerates pbars from injection to
  deposition orbit of the stacktail system
• Stochastic Cooling
• 2-4 GHz stacktail
• 2-4 4-8 GHz core momentum
• 4-8 GHz core transverse
• Increase particle density by factor of 5000
• Factor of 3-5 decrease in both transverse phase
  space dimensions
• Cycle Limit is clearing Deposition orbit

7
Quick Overview - Unstacking

• Stacking is halted
• Setup 120GeV beam line to 8GeV
• Check transmission and closure through line with
  reverse protons at 8GeV
• 4-5 pbar transfers
• Grow RF bucket in core and slowly accelerate beam
  to extraction orbit
• Kick beam into beam line to Main Injector then
  onto Recycler
• Reduction in time spent setting up and
  transferring beam
• More stacking hours per week

8
Stacking-to-Stacking Time
9
Improvements

• Beam lines orbit control
• New target module
• New Lithium lens
• Added Target Station collimator
• Installed vacuum Beam Stop
• Aperture in Debuncher and Accumulator
• 4-8GHz Core momentum cooling system Stacktail
  Stochastic cooling
• Equalizer

10
Orbit Control
Autotune/Feedback has been implemented to
compensate for power supply drift.
V
New BPM electronics
H
Before After
5mm
11
Target Station
Original Beam Stop removed 2004 shutdown
12
New Target Module lasts longer
13
Upgraded Lens Design

• Change of production process
• Stainless Steel to Titanium
• Electron welding to diffusion bonded

• Most failures are lithium getting into cooling
  water
• Weaken welds seen doing autopsies on old failures

Goal of 10,000,000 pulses at higher gradient
14
Target Station Yield to end of AP2
Each Target disk saw 6e18 protons Current new
style titanium body Li-lens has 3.5e6 pulses and
2.6e19 pot Pulsed Magnet has 5.1e6 pulses and
3.7e19 pot (best was 2.5e19 pot with 70 time
with new collimator best previous was 2.2e19pot)
15
AP2 Improvements

• Original Beam Stop slightly misaligned within
  shielding next to 120 GeV Proton Dump
• Aperture restriction
• Temporary Beam stop from switchyard installed
  during 2004 shutdown
• Held vacuum for a month
• Installed new Beam Stop during 2006 shutdown
• Remove multiple scattering from windows and 4m of
  air
• Installed two dipole trims to help with steering

16
AP2 Orbit Control
Autotune/Feedback has been implemented on this
beam line as well. Compensation for power
supply drift and thermal effects of the pulsed
devices of the target station
Before After
Before After
Horiz.
Vert.
10mm
17
Debuncher

• Previous work has increased the aperture
• Removal/modification of limitations
• Extraction kicker tube replacement is scheduled
  for next shutdown
• 5 increase acceptance of off momentum pbars
• Added orbit control
• Motorizing of components
• Extraction kicker stand last device to be
  motorized
• Will work on optimizing cooling

18
Accumulator Aperture

• Not optimal
• Have removed known problems (see below)
• Preparing to optimize orbit and change lattice
• Will be working on orbit

19
4-8GHz Core Trunk Changed

• Trunk changed from Coax to fiber
• Increase Bandwidth results in more effective
  cooling

20
Stacking Cooling Team

• Developed model and simulations of the different
  cooling systems of the Debuncher Accumulator
• Measurements and tests were done to verify model
• Gain ramps throughout stacking cycle
• Investigate core heating due to stacktail
• Reassigned 2-4GHz core and stacktail kicker tanks
• Stacktail and Core systems setups
• Stacktail bandwidth equalizer
• Led by Valeri Lebedev

21
Stochastic Stacking Stacktail

• Simon van Der Meer solution
• Constant Flux
• Static Solution
• Exponential Density Distribution generated by
  Exponential Gain Distribution
• Max Flux (W2hEd)/(f0p ln(2))

Log scale
Log scale
22
Stacktail Equalizer(s) on Paper
Present Feb07
23
Test Equalizer into Stacktail Medium Level
Test Equalizer built to confirm predictability of
model and gain experience before embarking upon
design and building of more complicated equalizer
24
Plans

• Stacktail Equalizer
• Optimized recently installed version
• Design and build better one based upon experience
  
• Accumulator Lattice Orbit
• Increase slip factor
• Better cooling performance
• Decrease lattice functions at limiting apertures
• 2-turn notch filters
• Debuncher transverse bands 3 4
• Switched in during stacking cycle
• Optimize gain ramps to cooling system
• Shorter cycle time
• 2.4s to 2.2s
• Optimize Lens gradient for pbar yield into
  Debuncher

25
Performance Comparison
26
Best Hour Stacking
27
Run 2 Antiproton Performance
Antiprotons (e10) in a week