Antiproton Study Periods

1
Antiproton Study Periods

• Keith Gollwitzer
• DOE Tevatron Operations Review
• March 21, 2006

2
Simplified Review of Operations/Studies Mode

• Stacking
• 120 GeV protons from MI through P1-P2-AP1
• Target producing secondaries
• Li Lens
• Negative 8.9 GeV/c secondaries transported via
  AP2 beam line
• Debuncher Ring to compress phase space (7x ?)2
  (50x ??) in 2s
• Transfer via D/A
• Accumulator stack pbars while compressing phase
  space (5x ?)2 build a core
• Reverse Protons
• 8GeV protons from MI
• Transfer line is P1-P2-AP1-AP3
• Circulate in Accumulator
• D/A transfer (really A/D)
• Circulate in (or partial turn through) Debuncher
• Extract up AP2 towards target station

3
Background

• We had reached the point where the
  instrumentation and orbit control made it
  possible to attempt
• Determining the orbit offset with respect to the
  center of the quadrupoles of the Debuncher ring
  and the AP2 beam line
• Correct the orbit to minimize the orbit-quad
  center offsets
• Set the AP2-Debuncher injection region
• Proposed two week period of studies
• Studies two shifts a day
• Third shift stack to support a lower luminosity
  collider program
• Set for early December

4
Execution Round 1

• TeVatron breaks on Monday Nov 21
• Scramble to find people for holiday weekend for
  start of studies
• First finished preliminary studies to set
  procedures to be used during studies period
• Institute third shift to investigate D/A beam
  line
• 15 days of reverse protons
• Debuncher beam-quad center offsets, orbit
  correction and centered devices about new orbit
• D/A beam line done on owl shifts
• AP2 Debuncher Injection region scanning and
  setting strengths of kicker and septum
• AP2 beam-quad center offsets orbit correction
• 4 days of stacking studies/start-up
• Steer secondaries beam onto AP2 reverse proton
  BPM positions
• Center Debuncher devices about beam
• General tune-up of kickers, RF, cooling systems,
  etc.

5
Preliminary Work

• Checkout of BPMs
• Preparation of timeline to acquire beam without
  much interruption to ? program
• Commissioning of TBT program for D/A into
  Debuncher for reverse protons
• Procedures for extracting reverse protons from
  the Debuncher into the AP2 beam line
• Attempt to minimize the effects of the Debuncher
  rotator cavities on the injected reverse protons

6
Commissioned Items

• Debuncher Reverse Proton Turn-By-Turn system
• Debuncher Reverse Proton partial turn extraction
  up AP2
• Debuncher Component Centering application
• Debuncher Orbit-Quad offset procedure
• AP2 Orbit-Quad offset procedure
• AP2 Beam Line Correction for reverse protons
• One-Shot Timeline for establishing circulating
  Debuncher beam
• Admittance measurements from data-logger
• Deb Heat Rev ps to AP2 sequencer aggregate
• Procedure for setting up the AP2-Debuncher
  Injection region
• Procedure for D/A Beam Based Alignment
• Accumulator local vertical bump at injection

7
Debuncher Work - 1

• Determination of orbit-quad center offset
• Change quad excitation and look for orbit change
• 68 quads have shunts
• 10 quads have ability to control excitation alone
• The rest are paired symmetrically about mid-point
  of straight section
• Concern about excitation of two quads at one time
  and determining offsets for each quad
• Did quad excitation orbits for nominal orbits as
  well as for two 1-bumps per plane
• Checked for consistency of change in offset
  determination with the change of orbit due to the
  1-bumps
• Vertical Orbit Correction
• Attempted global fit to minimize orbit-quad
  center offsets
• Re-checked orbit-quad center offsets no
  improvement
• Use of motorized quad stands as correction
  devices
• Local orbit corrections to minimize orbit-quad
  center offsets
• Re-check while working around the ring all lt1mm
  offset

8
Change in Debuncher Vertical Orbit

• Several places the orbit changed by 1cm
• Angle change at injection area
• All vertical trims and a majority of the
  motorized quad stands were used to perform the
  correction

9
Debuncher Work - 2

• Horizontal Orbit Correction
• Injection Region was only done
• Horizontal orbit-quad center offsets determined
• Centered motorized devices about orbit
• Total of 72 motors
• Lattice measurements were performed

10
Setting Injection Region

• Extracted beam up AP2 from Debuncher and
  determine orbit-quad center for the three
  down-stream most quads
• Determined horizontal closed orbit and AP2 orbit
  are centered in quads.
• Set vertical closed orbit to nestle under the
  septum
• Determine kicker strength to center beam in
  septum
• Determine septum strength to put beam in the
  center of the three AP2 quads

11
AP2 Work

• Able to have reverse protons every 15 seconds
• Determine downstream AP2 orbit-quad center
  offsets
• Not able to do upstream due to bussed quads and
  few BPMs to make offset determination
• Corrected orbit to minimize offset
• Summary of orbit changes for reverse protons
• Several places big changes, largest 2cm
• Large vertical angle at the end of AP2
• Lattice measurements
• Installed new lattice which believed to better
  match Debuncher

12
AP2 Orbit Change
13
Limiting Aperture

• Running wave pointed to Debuncher transverse
  Schottkys

Will be discussed more in next talk
14
Stacking Studies

• Steered secondaries to the vertical BPM positions
  found during the reverse proton studies
• Steered to horizontal downstream BPM positions
• Upstream, the momentum distribution affects the
  horizontal position
• Problems with AP2 orbit wandering
• Traced to 120GeV protons starting with Main
  Injector
• Associated with amount of time between cycles
• Consistent cycle time is best
• Developed auto orbit correction program
• Does 120GeV proton correction
• Then does AP2 secondaries correction
• Identified need for additional AP2 trims
• Centered Debuncher pickups

15
Orbit Wandering Stabilizing Orbit
V
Wandering
H
AP1
Horiz. AP2 Vert
10mm
10mm
V
5mm
H
Stabilized
16
Early January

• Wrote up results from the December studies period
• Prepared to install new AP2 trims
• Prepared to remove Debuncher transverse Schottkys
• Determined if had more Debuncher quad shunt
  freedom, then be able to change lattice
• Increase Debuncher admittance
• Removes Vertical Band 4 Arrays as limiting
  aperture
• Control was split for 6 pairs of quads

17
Middle of January

• Second TeV failure allowed for more dedicated
  time
• Installed two of four AP2 trims
• Obstruction search of AP2 beam pipe
• Removed Debuncher transverse Schottkys
• Tune measurements, main function, replaced by
  stochastic cooling pickups
• Reverse protons to correct horizontal Debuncher
  orbit to quad centers in straight sections
• Correction in arcs would lead to energy change
  that we were not prepared to do at the time
• Installed new Debuncher Lattice
• Small change to AP2 lattice for matching
• Centered Debuncher Devices about reverse proton
  orbit

18
More January

• TeV repair period allowed
• Running Wave identified the Extraction Kicker as
  the limiting aperture in both planes.
• Vertically bumped beam 2mm and essentially
  achieved goal
• Horizontally could bump beam 8mm and make
  admittance larger but bump in dispersion changes
  beam energy
• Await shutdown work to motorize the kicker stand
• Different horizontal orbit also affected
  Extraction
• Optimized Debuncher EXtraction bump for D/A
  transfers
• Ramp correctors near end of Debuncher stacking
  cycle so that cooled smaller beam is closer to
  septum when kicker fires
• Also tuned extraction kicker and septum strengths
  to steer beam in D/A beam line

19
February

• Intensity Studies
• Measurement of intensities through the stacking
  cycle
• Function of stack cycle time (see next talk)
• Function of proton intensity on target (see next
  slide)
• Also monitored proton beam quality
• Accumulator Cooling studies
• Stacktail and Core systems (future slide)
• Accumulator Aperture
• Investigation for less than two days (next talk)

20
Intensity study 4s cycle period
Cooling was optimized after each change of proton
intensity
Injected intensity into Accumulator
Intensity end of Debuncher cycle
Normalized to Beam on Target and 6 Booster turns
Early February
Intensity at end of AP2
Stacking rate
Many other diagnostics and settings were recorded
Flux to Accumulator is fine Look to
Accumulator Cooling
Proton beam on target
21
Stacktail System and the Core 4-8 GHz System

• Had been using 4-8 GHz system as a helper for the
  2-4 GHz core system. Decided it was time to move
  to 4-8 GHz.
• Because the 4-8 GHz core system runs at twice the
  frequency, the electrodes are ½ the size so the
  system has a factor of two smaller momentum
  reach.
• Moving the core closer to Stacktail to
  accommodate the smaller reach resulted in system
  instabilities at moderate stacks.
• Several attempts were made and we learned from
  each
• We now
• Use the 2-4 GHz core momentum system to augment
  the hand-off between the Stacktail and the 4-8
  GHz core momentum system
• Run the 4-8 GHz core momentum system at MUCH
  larger gain.
• Plans to increase the gain of the system
• Run the Stacktail during deposition debunching to
  pre-form the distribution to match the Stacktail
  profile
• Result 20.1 mA/hr

Early February
22
Stacking Performance
23
Stacking Performance
Best stacking for 1 hour for each day Average
Stacking rate for a week
24
Summary

• We were able to take advantage of the TeVatron
  failures
• Two long periods of studies
• Due to instrumentation and orbit control upgrades
  of the past few years, significant progress was
  done on the Debuncher admittance and progress
  made on the AP2 orbit
• How much? Next talk
• We understand how to keep the studies on track
  for the lengthy time period
• Three study chiefs met 2-3 times daily to access
  progress and direction
• See an almost 25 increase in stacking rate.