# Presentation: 196467

## Antiproton Study Periods

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

## 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

## 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

## 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.

## Preliminary Work

- Checkout of BPMs
- Preparation of timeline to acquire beam without much interruption to ν 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

## 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 p’s 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

## 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 <1mm offset

## 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

## 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

## 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

## 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

## AP2 Orbit Change

## Limiting Aperture

- Running wave pointed to Debuncher transverse Schottkys

- Will be discussed more in next talk

## 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

## Orbit Wandering – Stabilizing Orbit

- H

- H

- V

- V

- 5mm

- 10mm

- 10mm

- Wandering

- Stabilized

- AP1

- Horiz.              AP2             Vert

## 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

## 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

## 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

## 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)

## Intensity study – 4s cycle period

- Injected intensity into Accumulator

- Intensity end of Debuncher cycle

- Intensity at end of AP2

- Stacking rate

- Proton beam on target

- Normalized to Beam on Target and 6 Booster turns

- Cooling was optimized after each change of proton intensity

- Many other diagnostics and settings were recorded – Flux to Accumulator is fine – Look to Accumulator Cooling

- Early February

## 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 1⁄2 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

## Stacking Performance

## Stacking Performance

- Best stacking for 1 hour for each day
- Average Stacking rate for a week

## 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.**