Operating Procedure

Changes In PbarBrian DrendelJune 8, 2009

Antiproton Source Overview•Pulses of 120GeV proton beam, with intensity of

~8E12, from the Main Injector travel through the P1, P2 and AP1 beam lines, which total over 600m in length, every 2.2 seconds before striking a nickel alloy target.

•Downstream of the target, 8GeV negatively charged secondaries are collected and sent down the AP2 line, which is approximately 275m in length, before being injected into the Debuncher ring, where only antiprotons survive after the first hundred revolutions.

•The phase space density of the beam is increased by RF and stochastic cooling systems before the beam is transferred to the Accumulator via the D/A line just prior to the next stacking cycle.

•The Accumulator momentum stacks the 8GeV antiprotons while stochastic cooling systems further increase the phase space density of the beam.

•The collection of antiprotons in the Accumulator is called a stack.

•Once approximately 25x1010 antiprotons are accumulated in the stack, a portion of the 8GeV antiprotons are momentum sliced from the Accumulator core and sent through the AP3, AP1, P2, and P1 lines to the Main Injector and to the Recycler storage ring.

•Stacking Antiprotons is only paused momentarily during the actual transfer of Pbars out of the machine.

Pbar Performance•The rate at which

antiprotons are accumulated decreases as the stack size increases, and the optimal settings for the stochastic cooling systems change with beam intensity.

•This plot shows our stack rate (E10/hr) vs stack size (E10) over a number of years.

•Between FY05 and FY09, we can see•Peak stacking rate at

smaller stacks increased every year.

•Spend a higher percentage of time at smaller stacks, where we stack faster.

Pbar Performance•This plot shows our

weekly Antiproton accumulation. Each square represents how many Antiprotons were produced in one week.

•In January 2006, the most antiprotons produced in a week were 1,707.73 x 1010, or just under 250 x 1010 per day.

•In February 2009, the best week yielded 3,723.85 x 1010 antiprotons, which is over 530 x 1010 antiprotons per day.

•The Antiproton Source has doubled the maximum rate at which antiprotons are produced in the last three years.

PAC09 Papers•Improvements in Antiproton Production

are covered in three PAC09 Papers:•R. J. Pasquinelli, B. Drendel, K. Gollwitzer,

S. Johnson, V. Lebedev, A. Leveling, J. Morgan, V. Nagaslaev, D. Peterson, A. Sondgeroth, S. Werkema, et al., “Progress in Antiproton Production at the Fermilab Tevatron Collider”, PAC09 Paper TU6PFP075 (2009).

•B. Drendel, J.P. Morgan, D. Vander Meulen, “Operating Procedure Changes To Improve Antiproton Production at the Fermilab Tevatron Collider”, PAC09 Paper FR5REP030 (2009).

•J. Morgan, B. Drendel, D. Vander Meulen, “Improvements to Antiproton Accumulator to Recycler Transfers at the Fermilab Tevatron Collider”, PAC09 Paper TU6RFP032 (2009).

Antiproton Source

Department Papers

Automation Tools and Tuning Aggregates

•A number of improvements in Controls, Network Infrastructure, and Instrumentation have allowed the creation of a number of Automation Tools replace many manual tuning efforts.•Beam Line Tuner: Active beam line steering control using

BPMs20.•Core Babysitter: Core momentum cooling power

regulation•Debuncher Babysitter: Automatic recovery of tripped

Traveling Wave Tube power supplies.•Stacktail Monitor: Regulates stacktail momentum cooling

power via an ACL script.•Ion Flusher: Regulates Stabilizing RF for larger stacksAutomation

•Similar improvements have also allowed the creation of standardized tuning aggregates. Some aggregates are run parasitically while stacking, while others are done during periods of not stacking (called Standby). The aggregates ensure that the procedures are run in an optimal order. A few examples are:•Accumulator Tunes•Accumulator Core Signal Suppression•Kicker Timing alignment•Debuncher Momentum & Transverse notch filters•Debuncher Cooling power•Aligning Debuncher and Accumulator Energies•Centering movable devices.Standardized

Tuning

Automated Beam Line Tuning

•Beamline tuner corrects the 120 GeV orbit for protons in the P1, P2 and AP1 lines, as well as the 8 GeV secondaries in the AP2 line20. •During stacking, the Oscillation Overthruster reads in beam line Beam Position Monitor (BPM) data and alternates making corrections between the 120 GeV and 8 GeV beam lines.

•Trim magnets are used to correct both the 120 GeV proton and 8 GeV pbar orbits.

•If the 120 GeV BPM data is out of range, the 8 GeV correction reverts back to only using the two “target tune” trims until the 120 GeV BPM data is back in range.

•If the BPM data cannot be read, the BPM crates are reset to recover BPM functionality.

•During beam interruptions, corrections are temporarily delayed to allow the beam line elements to stabilize.

•P1, P2, AP1 & AP3 Beam Position Monitors talk over Ethernet to the control system6.•Designed to detect seven to 84 consecutive 53MHz proton bunches in reverse proton or stacking mode, and four 2.5MHz pbar bunches in Accumulator to Recycler antiproton transfer mode

•AP2, D/A Line & Debuncher BPMs also talk over Ethernet to the control system22.•Secondaries coming off the target have the same 53MHz bunch structure as the protons on target, but the intensity is very small.

•Intensities are on the order of 1E11 at the beginning of the line and 1E10 at the end of the line, with only about 2E8 reaching the Debuncher.

•One issue was lack of reliable network infrastructure to F23 and F27 service buildings.•F2 and AP0 have no unused fiber (10Mbit/s Thickwire networks).•F0 is the nearest fiber, but it is a long and expensive network run which would involve finding a cable path along the Tevatron berm.

•A unique cost-effective solution was employed that involves connecting to the controls network via 802.11b wireless Ethernet 2.

Accumulator Longitudinal Profile•VSA display of the Accumulator

Longitudinal profile during stacking10.•Beam is decelarated ~150MeV from the

Injection Orbit to the Core.•Injected beam is decelerated ~60MeV

from the Injection orbit to the edge of the stacktail by ARF1 in about 0.5 second.

•There are three Stacktail Momentum cooling legs the further decelerate another ~90 MeV to the Core over 10’s of minutes.

•Momentum and Transverse Stochastic Cooling systems cool the beam at the core.

•Green trace is when beam is first injected into the Accumulator.•Large amount of beam on the injection

orbit•Low frequency side of stacktail is cleared.

•Blue trace is after ARF1 moves beam from the injection orbit over to the deposition orbit (edge of the stacktail).•Beam left on the injection orbit is called

“leftover”•The Stacktail Momentum system must

clear the new beam from the low frequency side of the stacktail before the next pulse of beam.

Stacktail Monitor•The Stacktail Monitor is an

Accelerator Command Language (ACL) script that controls the Accumulator Stacktail Momentum system as follows:•regulates stacktail power

based on stack size based on operational experience,

•reduces stacktail power, if necessary, to control core transverse emittances,

•provides the core momentum target power levels used by the Core Momentum babysitter,

•turns off the Core 4-8 GHz momentum system when stacking beam is not being introduced to the stack, and

•sequentially turns off stacktail amplifiers to reduce heating if transverse emittances become excessive.

Trapped Ions

•The antiproton beam passing through the residual gas in the Accumulator vacuum chamber can create trapped positive ions, which may be related to periodic instabilities in the Accumulator at larger stack sizes.

•One mechanism to reduce trapped ions is to bunch the beam with a stabilizing RF system (ARF2).

•The plot on the left shows a typical large stack instability before our trapped ion flusher was implemented. •Accumulator Transverse emittances increase and beam

starts to fall out of the Accumulator. •Studies showed that modulating the ARF2 frequency and

changing the ARF2 voltage reduced the instabilities.

•The trapped ion Flusher is an Accelerator Command Language (ACL) script is used to improve beam stability in the Accumulator by changing the voltage and modulating the phase of the Stabilizing RF.

•This plot the flusher running with a large stack. In this case the Accumulator transverse emittances stay under control and we continue to stack antiprotons.

Automation Tools and Tuning Aggregates

•A number of improvements in Controls, Network Infrastructure, and Instrumentation have allowed the creation of a number of Automation Tools replace many manual tuning efforts.•Beam Line Tuner: Active beam line steering control using

BPMs•Core Babysitter: Core momentum cooling power

regulation•Debuncher Babysitter: Automatic recovery of tripped

Traveling Wave Tube power supplies.•Stacktail Monitor: Regulates stacktail momentum cooling

power via an ACL script.•Ion Flusher: Regulates Stabilizing RF for larger stacksAutomation

•Similar improvements have also allowed the creation of standardized tuning aggregates. Some aggregates are run parasitically while stacking, while others are done during periods of not stacking (called Standby). The aggregates ensure that the procedures are run in an optimal order. A few examples are:•Accumulator Tunes•Accumulator Core Signal Suppression•Kicker Timing alignment•Debuncher Momentum & Transverse notch filters•Debuncher Cooling power•Aligning Debuncher and Accumulator Energies•Centering movable devices.Standardized

Tuning

Tuning Aggregates•Tuning “Aggregates” made

for•When stacking•When not stacking

(Standby)•Ensures

•Items are tuned in the most efficient order.

•Improvements made possible by•Accelerator Command

Language Scripts

Debuncher Notch Filters

•Adjusting the Debuncher notch filters ensures that the beam leaving the Debuncher is centered on the correct frequency.

Optimize Debuncher Cooling Powers

•Automation Tools replace many manual tuning efforts.•Beam Line Tuner: Active beam line steering control using

BPMs (McGinnis’ Overthruster)•Core Babysitter: Core momentum cooling power regulation•Debuncher Babysitter: Automatic recovery of tripped

Traveling Wave Tube power supplies.•Stacktail Monitor: Regulates stacktail momentum cooling

power via an ACL script.•Ion Flusher: Regulates Stabilizing RF for larger stacks

•Improved tools are made possible by a number of factors, including:•ACL sciprts•Improvements in Instrumentation and controls.

•T

Accumulator Bend Bus

•Adjusting the Accumulator bend field so that the Core 2-4 GHz momentum notch is at the core revolution frequency.

Bend Field Matching•D/A VSA looks

at the Debuncher and Vertical Longitudinal Schottky detectors.

•Adjust the Debuncher bend field such that the Debuncher revolution frequency is the same as the Accumulator injection frequency.

ARF1 Tuning

•Next, adjust the Accumulator ARF1 to pickup the beam at the right frequency and optimize bucket size for stacking.

References•[1]B. Hendricks, “ACL – An Introduction” Fermilab Beams Documents Database

#929, July 2005, http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=929.

•[2]J. Morgan, B. Drendel, S. Johnson, “2009 Pbar Rookie Book,” Fermilab Beams Documents Database #2872, February 2009, http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=2872.

•[3] S. Werkema, Control of Trapped Ion Instabilities in the Fermilab Antiproton Accumulator, Proceedings of the 1995 Particle Accelerator Conference, p3397, May (1995).

•[4] S. Werkema, D. Peterson, and P. Zhou, Transverse Emittance Growth in the Fermilab Antiproton Accumulator with High-Current Antiproton

•[5] K. Gollwitzer, D. Peterson, J. Budlong, M. Dilday, D. Nicklaus, Patrick Sheahan, Antiproton Source Debuncher BPM using Synchronous Detection, Fermilab Beams Documents Database #1019, http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=1019, February, 13, 2004.

•[6] N. Eddy, E. Harms, Requirements for P1, P2, AP1, AP3, A1 line BPM upgrades, Fermilab Beams Documents Database #1279, https://beamdocs.fnal.gov/AD-private/DocDB/ShowDocument?docid=1279, September, 2004.

•[7] N. Eddy, Rapid Transfer BPM 53MHz Signal Expectations, Fermilab Beams Documents Database #1768, https://beamdocs.fnal.gov/AD-private/DocDB/ShowDocument?docid=1768, April, 2005.

•[8] N. Eddy, BPM Filter Module for Transfer Lines, Fermilab Beams Documents Database#1849, https://beamdocs.fnal.gov/AD-private/DocDB/ShowDocument?docid=1849, May 2005.

•[9] N. Eddy, Beam Monitoring and Control with FPGA Based Electronics, Fermilab Beams Documents Database# 2541, https://beamdocs.fnal.gov/AD-private/DocDB/ShowDocument?docid=2641, February, 2007.

•[10] D. McGinnis, Stacking Monitor and the 4-8GHz Thermostat. Fermilab Beams Documents Database#1942, http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=1942, August 30, 2005.

References•[11] K. Seiya et al., “Slip Stacking”, CARE-HHH-ADP workshop “BEAM07” Geneva,

Switzerland, October 1-5, 2007.•[12] M. Church and J. Marriner, “The Antiproton Sources: Design and Operation”,

Ann. Rev. of Nucl. And Part. Sci. 43: 253-295, December 1993.•[13] P. Hurh et al., “The Design of a Diffusion Bonded High Gradient Collection Lens

for the FNAL Antiproton Source”, PAC’03, Portland, Oregon•[14] V. Nagaslaev et al., “Measurement and Optimization of the Lattice Functions in

the Debuncher Ring at Fermilab” EPAC’06, Edinburgh, Scotland•[15] V. Lebedev et al., “Lattice Optimization for the Stochastic Cooling in the

Accumulator Ring at Fermilab”, COOL’07, Bad Kreuznach, Germany•[16] V. Nagaslaev et al., “8 GeV Beam Line Optics Optimization for the Rapid

Antiproton Transfers at Fermilab”, APAC’07, Indore, India•[17] R. J. Pasquinelli, “Superconducting Notch Filters for the Fermilab Antiproton

Source”, Proceedings of the 12th International Conference on High Energy Accelerators, pages 584-586, August 1983, Batavia, IL. 60510

•[18] J. Morgan et al., “Improvements to Antiproton Accumulator to Recycler Transfers at the Fermilab Tevatron Collider”, PAC09 Paper TU6RFP032 (2009).

•[19] R. Pasquinelli, et al., “Progress in Antiproton Production at the Fermilab Tevatron Collider”, PAC09 Paper TU6PFP075 (2009).

•[20] D. McGinnis, Care and Feeding of the Oscillation Overthruster, Fermi Beams Documents Database #2210, http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=2210.

•[21] B. Ashmanskas, S. Hansen, T. Kiper, D. Peterson, “AP2 line BPM system,” Instrumentation Techniques Talk, http://home.fnal.gov/~ashmansk/doc/ap2bpm_20050921.ppt, September, 2005.

•[22] B. Ashmanskas, et al., “FPGA-Based Instrumentation for the Fermilab Antiproton Source,” PAC’05, Knoxville, Tennessee (2005).