1. Fermilab Run 2 Accelerator Status and Upgrades
Keith Gollwitzer
Antiproton Source
Beams Division
Fermi National Accelerator Laboratory
October 8, 2003
Gollwitzer -- 8th ICATPP

2. Gollwitzer -- 8th ICATPP
Outline
Overview of the Fermilab Accelerator Complex
Status of Run 2
Comparison to Run 1
The last year of running
Overview of Upgrades for Run 2
Gollwitzer -- 8th ICATPP

3. Gollwitzer -- 8th ICATPP
Fermilab Overview
Proton source
CDF
Tevatron
Main Injector\
Recycler D0
Antiproton
source
Gollwitzer -- 8th ICATPP

4. Schematic of Accelerator Complex
Gollwitzer -- 8th ICATPP

5. Protons to the Tevatron
750keV Cockcroft-Walton
2 stage H- LINAC to 400MeV
Booster to 8GeV
Main Injector to 150GeV
Also 120GeV protons to pbar production target
Gollwitzer -- 8th ICATPP

6. Antiprotons to the Tevatron
120 GeV protons on Nickel target
Pulsed Lithium lens to focus secondaries beam
8GeV pbars collected in Debuncher
Transfer to Accumulator to further decrease phase space and accumulation of pbars
Transfer to Main Injector & ramped to 150GeV
Gollwitzer -- 8th ICATPP

7. Gollwitzer -- 8th ICATPP
Tevatron Beams
Inject 36 bunches of 150 GeV protons onto central orbit
Open helix using Electrostatic Separators
Inject 36 bunches of 150 GeV pbars onto second helical orbit
Accelerate beams to 980 GeV
Bring beam into collisions by modifying helices at detectors
Gollwitzer -- 8th ICATPP

8. Gollwitzer -- 8th ICATPP
Run II Milestones
September Main Injector commissioning begins
May 2000 – first attempts to unstack Pbars from the Accumulator
June 2000 – pbars extracted from Accumulator, accelerated to 150 GeV in the Main Injector
August GeV protons in the Tevatron re-established
August 2000 – Pbars in the Tevatron
October 2000 – 36 x 36 collisions achieved at 980 GeV
March Run II officially begins
August Initial luminosity 2.6 x 1031 cm-2s-1
Exceeds best of Run I
August 2003
4.88 x 1031 cm-2s-1 initial luminosity achieved
330 pb-1 integrated since Run II began
Gollwitzer -- 8th ICATPP

9. Gollwitzer -- 8th ICATPP
Peak Luminosity
Improved Beam Line Match
Helix Improvement
Accumulator Core Cooling
&Transfer Lattice
Improved TeV Closure
TeV Impedance
TeV Orbit Improved
Improved Transfers
Gollwitzer -- 8th ICATPP

10. Integrated Luminosity
Variations are a function
store hours (reliability)
Gollwitzer -- 8th ICATPP

11. Gollwitzer -- 8th ICATPP
Parameter List
RUN
Ib ( )
6 x 6
Run II (2003)
(36 x 36)
Current best
Protons/bunch
2.3 X 1011
2.7
Antiprotons/bunch
0.55 x 1011
0.3
0.2
Total Antiprotons
3.3 x 1011 11
7.2
Pbar Production Rate
6.0 x 1010/hour 18
13.5
Proton Emittance
23p mm-mrad
20p
Antiproton Emittance
13p mm-mrad
15p b*
35 cm 35
Energy
900 GeV
1000
980
Bunch Length (rms)
0.60 meter
0.37
~0.60
Typical Luminosity
1.6 x 1031cm-2s-1
8.6
4.9 best-to-date
Integrated Luminosity
3.2 pb-1/week
10.9
9.6 best-to-date
Bunch spacing
~3500 nsec
396
Gollwitzer -- 8th ICATPP

12. What could be Better & Fixes
Tevatron Performance
Coupling of transverse motion is large
Major source identified in dipoles (see slides)
Stability control
Removal of unused Lambertson decreased machine impedance
Adding vacuum liner to remaining Lambertsons
Cu-Be bronze: high electrical & thermal conductivities
Limited orbit control
Vertical correctors running near maximum due to roll of dipoles
Resetting many magnets during current shutdown
Gollwitzer -- 8th ICATPP

13. Gollwitzer -- 8th ICATPP
Tevatron Coupling
Data shows in-plane and out-of-plane difference orbits after single horizontal kick. Data is for 1st 5 turns in Tevatron.
Coupling in Tevatron is ~uniform around the ring and is consistent with ~1.5 units of a1 per dipole. This is compensated by a distributed skew quad circuit of 42 elements.
Gollwitzer -- 8th ICATPP

14. Tevatron Coupling (continued)
Tevatron dipole cross section
Tevatron coil and cryostat assembly is held within the iron by 4 supports at 9 locations along the length of the magnet. Recent measurements of the “smart bolts” (upper supports) on magnets in the tunnel, indicate that the coil assembly has sagged by ~2 mils from original. This is enough to produce ~1 unit of a1 per dipole.
In 1984, compensating skew quad circuit was running at ~2A. From 1995 compensating skew quad circuit has been running at ~24A 800 GeV).
Gollwitzer -- 8th ICATPP

15. What could be Better & Fixes
More particles to collisions
Overall transmission efficiency 55-65%
N stages each 90%
Work to increase each stage to 95% efficiency 70-80%
More Antiprotons
Longer stores -- accumulation of more pbars
Tevatron stores ending unintentionally
Want to increase stacking rate (see slides)
Improve phase space compression in Antiproton Source
More protons on target
Better collection of antiprotons.
Gollwitzer -- 8th ICATPP

16. Antiproton Stacking 20 Antiproton produced per 10e6 on target
Stacking Rate (mA/hr) 10
Largest Stack to Date 236mA
Stack Size (mA)
Gollwitzer -- 8th ICATPP

17. Antiproton Stack Process
Accumulator Stacktail Cooling
Process
Debuncher beam is transferred to the Injection Orbit
Bunched with RF
Moved with RF to Deposition Orbit
Stacktail pushes and compresses beam from the Deposition Orbit to the Core
Core Momentum systems gather and further compresses
Transverse systems also compress phase space of beam
The Problem
Pulse rate determined by speed Stacktail can move beam off Deposition Orbit
Amount needed to move dependent upon incoming longitudinal width
Debuncher needs to compress the beam smaller before transfers
Gollwitzer -- 8th ICATPP

18. Plan for Higher Luminosity
Luminosity Formula:
Dominant Terms:
Number of pbars
Proton Brightness
The other terms we have little ability to change
Essentially at limit of number of protons/bunch
Strategy is to increase the number of pbars
Increase protons on target & production efficiency
Increase capability to handle pbar flux
Need to control Tevatron Beam-Beam effects
Gollwitzer -- 8th ICATPP

19. More Protons on Production Target
Quantity
Slip Stacking will nearly double beam on target
Quality
Bunch length is passed on to the pbars
Smaller helps in RF capture of pbars
Smaller emittance helps collection
Target
Increase of energy deposited in target
Investigating new target materials
Beam sweeping to move beam spot during spill
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20. Gollwitzer -- 8th ICATPP
Slip Stacking Cartoon
(1)
(2)
(3)
(1) Booster batch (2) Batch 1 in MI. (3) RF system A accelerates beam while Booster batch 2 is prepared. (4) Inject batch 2 into MI. (5) Decelerate batch 2 with RF system B. (6) Allow batches to slip until lined up; capture both batches with RF system C while turning off RF systems A&B.
(4)
(5)
(6)
Gollwitzer -- 8th ICATPP

21. Collect More Antiprotons
Increase pbar yield
Increase gradient of collection lens
Increase the admittance of the transfer line and Debuncher ring
Yield = pbar/proton on target
Gollwitzer -- 8th ICATPP

22. Higher Gradient Lithium Lens
Trade off between gradient and lens lifetime
Nearly same design with improvements
Cooling, Diffusion bonded, new Titanium Alloy
Gollwitzer -- 8th ICATPP

23. Increase Antiproton Acceptance
Most elements in 300m beam line and 500m Debuncher ring should handle 40 mm-mrad
Identifying and taking corrective action
Beam-based alignment
Adding corrector elements to current limit set
Improving diagnostics and procedures
Gollwitzer -- 8th ICATPP

24. How to handle the increased pbar flux
Optimize Debuncher cooling systems
Change Accumulator Stacktail system to push more flux
Consequence smaller core
Hence need another place to accumulate pbars
Recycler Ring in Main Injector tunnel
Stochastic cooling will not be sufficient
Electron cooling at 8GeV
Gollwitzer -- 8th ICATPP

25. Gollwitzer -- 8th ICATPP
Recycler Ring Status
Slowly being commissioned over the last few years while operating Run 2
Little tunnel access time
Main magnets are permanent magnets
Recent addition of surplus LEP correctors
Better orbit control particularly when the Main Injector ramps
Current shutdown will finish all vacuum work
Stacking is done using barrier RF buckets
Electron cooling will be main cooling system
Installation next Spring/Summer
Final commissioning and integration into operations over the next 1.5 year
Gollwitzer -- 8th ICATPP

26. Overview of Electron Cooling
Co-moving low emittance electron beam cools pbars
First use at medium energy
High current with strict electron beam requirements for the 20m cooling section
Gollwitzer -- 8th ICATPP

27. Electron Cooling Parameters
Emphasis on longitudinal cooling; transverse free & assume incoming 3 mm-mrad (normalized) and 10 eV-sec
Electron Beam Current
500 mA
Pelletron Voltage
5 MV
Allowed Voltage Ripple
500 V
Electron Beam Size
3 mm
Angular Electron Beam Spread
0.22 mrad
Electron Beam alignment
0.1 mrad
Solenoid Length
20 m
Solenoid Field
100 G
Longitudinal Cooling Rate
55 eV-sec/hr
Longitudinal Cooling Time
25 min
Time between Input transfers
30 min
Final Longitudinal emittance
50 eV-sec
Gollwitzer -- 8th ICATPP

28. Beam-Beam Interactions
Near misses: mainly,on each side of the interaction region
Effect of beams on each other is a series of focusing events causing the tune to change
Current Nproton = 10Npbar Future Nproton = 2Npbar
Gollwitzer -- 8th ICATPP

29. Gollwitzer -- 8th ICATPP
Beam-Beam Issues
What to do about spread in tunes due to Beam-Beam Interactions
Increase Electrostatic Separator strength to increase orbit separation
Beam-Beam Compensation
Electron Lens
High Current Wires
Gollwitzer -- 8th ICATPP

30. Tevatron Electron Lens
Can modulate electron beam for each pbar bunch (& abort gap)
Installed in TeV
Used mainly for keeping abort gap clear by driving particles to a strong resonance
Have demonstrated decrease rate of emittance blow-up for single pbar bunch
A second lens is needed for full BBC
Gollwitzer -- 8th ICATPP

31. Wires Beam-Beam Compensation
An R&D project
Current thought is to have 4 stations
At each station, 4 wires
Each wire with 200A
Prototype later this fall
Prototype station ready for 2004 summer shutdown installation
Gollwitzer -- 8th ICATPP

32. Gollwitzer -- 8th ICATPP
Draft Run 2 Schedule
Gollwitzer -- 8th ICATPP

33. Gollwitzer -- 8th ICATPP
Parameters of Upgrade
Gollwitzer -- 8th ICATPP

34. Gollwitzer -- 8th ICATPP
Tevatron Reliability
Analysis of number of store hours between Tevatron failures
Failures occur randomly
Rarely are failures correlated
For any hour of store: failure probability is 2.5%
Many possible components can fail: implies the mean lifetime of Tevatron components is ~5yr
Gollwitzer -- 8th ICATPP

35. Gollwitzer -- 8th ICATPP
Summary
Fermilab Run 2 Progresses
Accelerator complex in 2 years has delivered twice as much integrated luminosity as Run 1
Still work to be done in improving operations and understanding the accelerator complex
Run 2 Upgrades to be done over the next 3yr
Increase weekly integrated luminosity: factor 5.5
Mostly comes from increased number of Antiprotons
Increased stacking rate requires the Recycler Ring with Electron Cooling
Will require understanding and mitigating Beam-Beam effects
Gollwitzer -- 8th ICATPP