Wolfram Fischer 28 July 2010 Fermilab Accelerator Advisory Committee Meeting Content Headon beambeam compensation for RHIC LHC RHIC luminosity goals and electron lenses LHC beambeam compensation ID: 783281
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Slide1
Electron lens studies
in support of RHIC / LHCWolfram Fischer
28 July 2010Fermilab Accelerator Advisory Committee Meeting
Slide2Content
Head-on beam-beam compensation for RHIC / LHCRHIC luminosity goals and electron lensesLHC beam-beam compensationProposed Tevatron studies
Electron lenses with Gaussian transverse profileParametric scans to investigate tolerance to errorsPbar tune footprint compression
Pbar lifetime without BB / with BB / with BB+lensTest of instrumentation (bremsstrahlung monitor)Wolfram Fischer
2
Slide3Wolfram Fischer
3 2 superconducting 3.8 km rings2 large experiments
100 GeV/nucleon Au 250 GeV polarized protonsPerformance defined by
1. Luminosity L 2. Proton polarization P 3. Versatility Au-Au, d-Au, Cu-Cu, polarized p-p (so far)
12 different energies (so far)
Relativistic Heavy Ion Collider
1 of 2 ion colliders
(other is LHC)
, only polarized p-p collider
Slide4RHIC polarized protons – luminosity and polarization
Wolfram Fischer4
Lpeak = 85x1030
cm-2s-1Lpeak
= 50x10
30
cm
-2
s
-1
FOM
=
LP
4
(longitudinally polarized beams)
Slide5Wolfram Fischer
5RHIC luminosity and polarization goals
Parameter
Unit
Achieved
Enhanced
design
Next
L
upgrade
Au-Au operation
(2010)
(>=2012)
Energy
GeV/nucleon
100
100
100
No of bunches
…
111
111
111
Bunch intensity
1091.11.01.0Average L 1026cm-2s-120840p- p operation(2009)(>=2011/12)(>=2014)Energy GeV100 / 250100 / 250250No of bunches …109109109Bunch intensity 10111.3 / 1.11.3 / 1.52.0Average L 1030cm-2s-124 / 5530 / 15060 / 300Polarization P %55 / 347070
Source upgrade (
N
b increase) and electron lens (x)
Slide6Electron lenses in RHIC – under construction
Wolfram Fischer6
IP8 -IP
10 Dyy = 10.9 p
IP6-
IP
10
Dy
x
= 19.1
p
Basic idea:
In addition to 2 beam-beam collisions with
positively
charged beam have another collision with a
negatively
charged beam with the same amplitude dependence.
2 electron lenses installed in Tevatron,
not used for head-on beam-beam compensation
Exact compensation possible for:
short bunches
Dyx,y = kp between p-p and p-e collision no nonlinearities between p-p and p-e same amplitude dependent kick from p-p, p-eOnly approximate realization possibleIPAC2010 papers: MOPEC026 (overview), THPE100 (long bunches), Y. Luo TUPEC082 (SimTrack), THPE102 (simulations), C. Montag MOPEC035 (beam alignment with bremsstrahlung), C. Montag TUPEB050 (e-lens for e-beam)
Slide7Electron lenses in RHIC – under construction
Wolfram Fischer7
e-beam
p-beam
partial compensation of head-on beam-beam
goal of 2x luminosity increase together with source upgrade
(allowing for higher bunch intensity with good polarization)
critical: relative beam alignment
(Tevatron experience)
requires straight solenoid field lines, good instrumentation
(
bremsstrahlung
monitor –
C. Montag MOPEC035)
DC gun: 7 kV, 0.6 A
6 T solenoid, straightness
~0.1 rms beam size
collector
Slide8Electron lenses in RHIC – under construction
Wolfram Fischer 8 6D beam lifetime simulation of electron lens (Y. Luo, THPE102)
N
b = 3x1011without and with e-lens
Simulations show
full benefit of e-lens
for N
b
> 2x10
11
(i.e. with source upgrade)
Beam lifetime
simulations are
challenging –
require good model
and supercomputer
Slide9Beam-beam compensation in LHC
Beam-beam in LHCTotal beam-beam parameter in LHC: x = 0.01 (3 IPs, design)3 head-on collisions, 18 or 19 long-range collision
on each side of every IPLong-range compensationSpace is reserved for long-range wire compensators
(about 100 m from IP, location with bx = by)Wire experiments done in SPS, RHIC; wire compensation in DAFNE
Head-on compensation
Could use same space as wire location
Would allow increase in bunch intensity as a possible upgrade
Wolfram Fischer
9
Ph.D. Thesis,
G. Sterbini, 2009
Slide10Location for beam-beam compensators in LHC
Wolfram Fischer10
IP
s = 13329 mbx = 0.55 m mx = 32.049 [2p]by = 0.55 m
m
y
= 29.604 [2
p
]
BBLR or e-lens
s = 13433 m
b
x
= 1925 m
m
x
= 32.303 [2
p
]
b
y
= 1784 m
m
y
= 29.857 [2p]Dmx = 91Dmy = 91
Slide11Simulation for LHC (LARP Collaboration Meeting, April 2010)
Wolfram Fischer 11
Slide12Wolfram Fischer
12 A. Valishev, LARP CM14
Slide13Tevatron electron lens studies
Gaussian transverse electron beam profile for all measurements (Gaussian gun to be removed next week, may ask for reinstallation)Quantify tolerances for a number of quantities:Beam offset
Crossing angle(Spurious) dispersion
Electron beam currentElectron sizeTolerances:Within tolerance pbar beam lifetime acceptableStatic or time-dependent (harmonic, noise)
excursions of
above quantities
[All studies provide input for benchmark simulations.]
Wolfram Fischer
13
Slide14Tevatron electron lens studies
2 Golden experiments:Demonstrate reduction in pbar footprint with electron lensMeasure pbar lifetime Without beam-beam interaction (large)With beam-beam interaction (small)With beam-beam interaction and electron lens (large again?)
(Measuring pbar tune distribution with protons present difficult – 21 MHz Schottky not gated for bunches.)
Some experiments done already – not all fully analyzed.Wolfram Fischer
14
Slide15Gaussian Gun
Up to 1A current with the new modulator (Ne=2x1011)
Installed in TEL-2 on June 20 (Tevatron shutdown 6/15 – 9/11)A.Valishev, Tev Acc Studies Wkshp
Collector current
Courtesy A. Valishev, CM14
Slide16BPM Readout
Old LabView program slowNew Java program faster (response time ~20 s), uses simpler algorithmShorter e- pulse with new generator – closer calibrations and offsets for electrons and protons/pbars1/13/2010
A.Valishev, Tev Acc Studies Wkshp16
Courtesy A. Valishev, CM14
Slide17Wolfram Fischer
17 Courtesy A. Valishev, CM14
Slide18Wolfram Fischer
18 Courtesy A. Valishev, CM14
Slide19Wolfram Fischer
19 Courtesy A. Valishev, CM14
Slide20Test of bremsstrahlung monitor
Wolfram Fischer 20
Plan to use bremsstrahlung to align p and e beams in RHIC
C. Montag, D. Gassner et al. IPAC2010 Would like to test detectors Tevatron
Waiting for opportunity to install
Slide21Test of bremsstrahlung monitor in Tevatron
Wolfram Fischer 21
Micro Channel PlateTectra MCP-18-D-R-AMCP (assembly diameter = 30mm)Diameter MCP sensitive area = 18mm
Number of MCP's = D = DoubleMount type = S = ShortReadout = A = AnodeOptions = Ring or Grid
Slide22Tevatron studies
Also interested in:Studies with hollow electron beam (different e-beam edge)Coherent beam-beam modesWolfram Fischer
22
Slide23Wolfram Fischer
23
Slide24Wolfram Fischer
24
Slide25Summary
RHIC electron lenses under construction for head-on beam-beam compensationHead-on beam-beam compensation is a possible upgrade for the LHC (location available, some simulations done)
Tevatron studies with electron lenses for RHIC / LHCUntil RHIC lenses are completed (end of 2012), TELs are the only available test devices for head-on beam-beam compensation
Primarily interested in Gaussian profile ( reinstallation)After quantitativ analysis of experiments done, may ask for further test
(parametric
scans to investigate tolerance to errors
; Pbar
tune footprint compression, lifetime without BB / with BB / with
BB+lens
)
Test of bremsstrahlung
monitor
(
profile not critical
)
Wolfram Fischer
25
Slide26Acknowledgment
Wolfram Fischer 26 Fermilab staff is extremely helpful in the RHIC electron lens design, collaboration on beam-beam
simulations, and electron lens experiments in the Tevatron.V. Shiltsev, A. Valishev, H.J. Kim, G. Kuznetsov,
A. Romanov, G. Saewert, T. Sen, G. Stancari, X. ZhangAlso: A. Kabel (SLAC), J. Qiang (LBNL)