electron cooling of 8 gev antiprotons at fermilab’s recycler: results and operational implications...
TRANSCRIPT
-
Electron cooling of 8 GeV antiprotons at Fermilabs Recycler:Results and operational implications June 5th, 2006L. Prost, Recycler Dpt. personnelFermi National Accelerator Laboratory
Lionel PROST, et al.
-
OutlineContext of electron cooling at FNALElectron coolingElectron beam propertiesCooling of antiprotonsCooling force measurementsElectron cooling in operationConclusion
Lionel PROST, et al.
-
Fermilab complexThe Fermilab Collider is a Antiproton-Proton Collider operating at 980 GeV
Lionel PROST, et al.
-
Antiprotons and LuminosityThe strategy for increasing luminosity in the Tevatron is mostly to increase the number of antiprotonsProvide a third stage of antiproton cooling with the Recycler
Lionel PROST, et al.
- Antiprotons flow (Recycler only shot)Keep Accumulator stack
-
Beam Cooling in the RecyclerThe missions for cooling systems in the Recycler are:The multiple Coulomb scattering (IBS and residual gas) needs to be neutralizedThe emittances of stacked antiprotons need to be reduced between transfers from the Accumulator to the RecyclerThe effects of heating because of the Main Injector ramping (stray magnetic fields) need to be neutralized
Lionel PROST, et al.
-
Performance goal for the long. equilibrium emittance: 54 eV-sGOALMAXStochastic cooling limit20% lower36 bunches at 2 eVs per bunch36 bunches at 1.5 eVs per bunch
Lionel PROST, et al.
-
Recycler Electron CoolingThe maximum antiproton stack size in the Recycler is limited byStacking rate in the Debuncher-Accumulator at large stacksLongitudinal cooling in the RecyclerStochastic cooling only~1401010 for 1.5 eVs bunches (36)~1801010 for 2eVs bunches (36) Longitudinal stochastic cooling has been complemented by Electron cooling
Lionel PROST, et al.
-
How does electron cooling work?In the moving frame we have a mixture of gases of hot antiprotons and cold electrons. Transfer of energy through Coulomb interactions
Lionel PROST, et al.
-
How does electron cooling work? (cont)At electron energies up to ~300 keV:Direct electrostatic acceleration of electrons with energy recovery.A strong longitudinal magnetic field accompanies electrons from the cathode to the exit of the cooling section. Magnetic field assures the transport of the electron beam while retaining low temperature of the electrons.Typical parameters of all existing low-energy electron coolers:electron kinetic energy: 2-300 keVelectron beam current: up to 5 ACooler length: 1-3 mMagnetic field: 0.1-0.5 T
Lionel PROST, et al.
-
What makes the Fermilab system unique? It requires a 4.36 MV DC power supply. We have chosen a commercially available electrostatic accelerator. As a consequence we had to develop several truly new beamline, cooling, and solenoid technologies:Interrupted solenoidal field: there is a magnetic field at the gun cathode and in the cooling section, but no field in between. It is an angular-momentum-dominated transport line;Low magnetic field in the cooling section: 50-150 G. Unlike low-energy coolers, this will result in non-magnetized cooling something that had never been tested;A 20-m long, 100-G solenoid with high field quality
Lionel PROST, et al.
-
Fermilab cooler main featuresElectrostatic accelerator (Pelletron) working in the energy recovery modeDC electron beam100 G longitudinal magnetic field in the cooling sectionLumped focusing outside the cooling section
Lionel PROST, et al.
Electron energy
MeV
4.338
Beam current used for cooling
A
0.05 - 0.5
Magnetic field in CS
G
105
Beam radius in the cooling section
mm
2.5 - 5
Pressure
nTorr
0.2 - 1
Length of the cooling section
m
20
-
Electron cooling system setup at MI-30/31Pelletron(MI-31 building)Cooling section solenoids(MI-30 straight section)
Lionel PROST, et al.
-
Commissioning Milestones Highlights (2005)Feb, 25th Installation CompleteMar, 7th All systems ready for commissioningCharging system, gun, pulser workMar, 17th 4.3 MeV, 0.5 A pulsed beam to collector (U-Bend mode, low losses)Regulation system works properlyApr, 20th First DC beam (few mA) in Recycler beam lineJun, 3rd 4.3 MeV, 0.2 A DC recirculating in the full line. Jul, 9th First observation of electron beam interacting with antiproton beamJul, 15th Electron Cooling of 8 GeV antiprotons has been demonstrated Jul, 16th Electron cooling is used for a collider shotJul, 26th 0.5 A DC in the full line. All commissioning milestones are met.
Lionel PROST, et al.
-
Beam quality: Longitudinal temperatureThe cooling process is determined by an effective energy spread consisting primarily of two components, the electron energy spread at a fixed time and the Pelletron voltage rippleThe energy spread is determined by IBS (the main contributor) and by density fluctuations at the cathode. According to simulations, at currents 0.1 0.5 A the energy spread is 70 150 eV. The Pelletron voltage ripple is 200 - 300V r.m.s. (probably, fluctuates from day to day). The main frequency is 1.8 Hz, which is much shorter than a cooling time. Hence, the effective energy spread is equal to these two effects added in quadratures.
Lionel PROST, et al.
-
Beam quality: Electron angles in the cooling section *Angles are added in quadrature
Lionel PROST, et al.
Component
Upper limit, (rad
Present estimation, (rad
Diagnostics
Comments
Temperature
90
70
OTR + pepper pot
Aberrations
90
50
30
Simulated
BPMs
@ 1 mm (rms)
Envelope scalloping
100
120
Movable orifices (scrapers)
For the 0.5 A beam boundary at 10-5 level of losses
Dipole motion caused by magnetic field imperfections
100
40
Magnetic measurements + BPMs
Beam motion
50
40
BPMs
With a slow feedback
Drift velocity
20
20
Calculated
For I =0.5 A
Total
200*
160
- Back one year ago July 05 electron beam statusGoal for the rms angular spread (
-
First e-cooling demonstration 07/15/05
Lionel PROST, et al.
-
Cooling force Experimental measurement methodsTwo experimental techniques, both requiring small amount of pbars (1-5 1010), coasting (i.e. no RF) with narrow momentum distribution (< 0.2 MeV/c) and small transverse emittances (< 3 p mm mrad, 95%, normalized)Diffusion measurementFor small deviation cooling force (linear part)Reach equilibrium with ecoolTurn off ecool and measure diffusion rateVoltage jump measurementFor momentum deviation > 2 MeV/cReach equilibrium with ecoolInstantaneously change electron beam energyFollow pbar momentum distribution evolution
Both methods characterize the effectiveness of electron cooling (hence, the electron beam quality) quite locally and not necessarily the cooling efficiency/rate for large stashes
Lionel PROST, et al.
-
Example: 500 mA, nominal settings, +2 kV jump (i.e. 3.67 MeV/c momentum offset), on axis Traces (from left to right) are taken 0, 2, 5, 18, 96 and 202 minutes after the energy jump.~3.7 MeV/c2.8 1010 pbar3-6 p mm mrad
Lionel PROST, et al.
-
Extracting the cooling (drag) force15 MeV/c per hourEvolution of the weighted average and RMS momentum spread of the pbar momentum distribution function
Lionel PROST, et al.
-
Cooling force measurements carried outThree types of measurements: Various electron energy jumpsDescription of the drag rate as a function of the antiproton momentum deviationFor various electron beam positionsVarious electron beam positions (w.r.t. antiproton beam)Mostly at 100 mAVarious electron beam currentOn axis (mostly) i.e. electron beam and antiproton beam are centeredBy-productDrag rate as a function of the transverse emittanceKeeping the transverse emittance low throughout the measurement has been sometimes challengingDifficulties measuring the real emittance at very low Dp/p and low number of particles
Lionel PROST, et al.
-
Drag Force as a function of the antiproton momentum deviation100 mA, nominal cooling settingsError bars statistical error from the slope determination
Lionel PROST, et al.
-
Electron cooling drag rate - TheoryFor an antiproton with zero transverse velocity, electron beam: 500 mA, 3.5-mm radius, 200 eV rms energy spread and 200 rad rms angular spreadNon-magnetized cooling force modelLab frame quantities
Lionel PROST, et al.
-
Comparison to a non-magnetized modelConstant:Coulomb log, L = 10Fitting parameters:Electron beam current density, JcsLab frame RMS energy spread, dELab frame RMS angular spread, qe100 mA, nominal cooling settings (both data sets)
Lionel PROST, et al.
-
Comparison to a non-magnetized model (cont)Results from the fitsRMS energy ripple, RMS angular spreadBest estimations (250 eV, 160 mrad) from measurementsBeam current densityFactor of ~5 higher than best estimate (assuming uniform current density)
Electron beam vertical offset, mm01.52JCS, A cm-21.20.70.3qe, mrad0.190.250.25dE, eV370370370
Lionel PROST, et al.
-
Better model for determining the current density in the cooling section ?For 100 mA, the beam current density distribution is NOT uniformUse SuperSAM gun simulations to estimate on-axis current densityElectron beam is quite uniform and linear (in phase space) over a limited emitter surfaceThis model reduces the discrepancy between measured and expected current density in CS by a factor of ~2
Lionel PROST, et al.
-
Electron cooling in operationIn the present scheme, electron cooling is typically not used for stacks < 200e10Allows for periods of electron beam/cooling force studiesOver 200e10 storedElectron cooling used to help stochastic cooling maintain a certain longitudinal emittance (i.e. low cooling from electron beam) between transfers or shot to the TeV~1 hour before setup for incoming transfer or shot to the TeV, electron beam adjusted to provide strong cooling (progressively)This procedure is intended to maximize lifetime
Lionel PROST, et al.
-
Electron cooling in operation (cont)Electron coolingprior to extractionStochastic cooling onlyElectron cooling between transfersTransverse emittance 3 p mm mrad/divMomentum spread 1.25 MeV/c /divLongitudinal emittance 50 eVs/divPbar intensity 75e10/div
Lionel PROST, et al.
-
Electron cooling between transfers/extractionElectron beam is moved inStochastic coolingafter injectionElectron beam out (5 mm offset)Electron beam current 0.1 A/divTransverse emittance 1.5 p mm mrad/divElectron beam position 1 mm/divLongitudinal emittance (circle) 25 eVs/divPbar intensity (circle) 16e10/div~1 hour100 mA195e10~60 eVs
Lionel PROST, et al.
-
Adjusting the cooling rateTwo knobsElectron beam currentBeam stays on axisDynamics of the gun varies between low and high currentsHence, changing the beam current also changes the beam size and envelope in the cooling section Electron beam positionAdjustments are obtained by bringing the pbar bunch in an area of the beam where the angles are low
5 mm offset2 mm offsetArea of good cooling
Lionel PROST, et al.
-
Issues related to electron cooling and large stacksSince started to use the electron beam for cooling, we have dealt with two main problemsTransverse emittance growthDuring mining Lifetime degradationWhen the beam is turned on and/or moved towards the axis (i.e. strong cooling)MINING
Lionel PROST, et al.
-
Emittance growth during miningEmittance growth likely due to a quadrupole instability (Burov et al. )Growth rate kxy Ie Ip , (kxy coupling parameter)Increase tune split to reduce kxy0.414/0.418 (H/V) 0.451/0.468 (H/V)(A)(B)Initial growth rate: (A) 36 p mm mrad per hour(B) 3 p mm mrad per hour/ ~10
Lionel PROST, et al.
-
Lifetime degradation throughout a storePbar intensityLifetime (1 hour running average)500 hours60 1010400 hours
Lionel PROST, et al.
-
Present Recycler performance with electron cooling
Lionel PROST, et al.
-
Evolution of the number of antiprotons available from the Recycler (~1 year period)Mixed mode operationEcool implementationRecycler only shots
Lionel PROST, et al.
Chart1
42
47
85
90
91
54
56
78
67
74
89
37
37
45
45
49
49
91
91
72
71
71
69
70
71
71
86
86
81
81
68
16
57
48
78
64
85
92
98
91
43
76
65
70
63
56
124.1
113
166
51
74
58
39
108
60
116
90
138
124
121
143
144
44
66
138
94
56
69
58
14
16
59
7
33
32
42
45
49
47
65
52
128
85
51
59
74
43
71
95
30
90
32
62
106
83
53
100
81
58
61
60
94
109
51
46
92
137
116
111
Ecooling
59.5
90.7
30.6
85
48
100
60
100
143
126
59
59
89
85
92
81
97
116
112
137
111
182
46
41
98
110.5
143
60
109
64
70
136
70
113
165
129
134
141
142
216
241
90
55
69
77
225
280
235
257
183
153
209
117
197
228
111
168
191
219.57
223
285
247
266
320
220
256
89
171
248
204
200
300
248
252
174
99
132
77
181
72
55
163
219
288
236
137
270
255
273
260
354
326
323
289.7
284
198
154
115
127
182
30
107
176
201
139
209
181
334
258
258
418
197
131
150
283
166
243
Number of antiprotons (x 1010)
Sheet1
data
DateIntensityLong emittance 90%Long emittance 95%RMS mom spread90% mom spreadBucket lengthTrans emittanceNotes
2/14/041.88E+0114.018.215linear ramp, two bunches
4/7/041.60E+017.09.13.36linear ramp,single bunch
2/20/041.20E+0263.081.95.37Barrier bucket
3/12/043.50E+0121.027.32.37Barrier bucket
3/14/047.80E+0151.061.23.110.54.87Barrier bucket
3/25/043.57E+0131.938.32.89.23.33Barrier bucket
4/7/041.60E+017.09.23.511.70.36Barrier bucket
4/8/043.10E+0111.314.33.70.67Barrier bucket
4/12/045.20E+0120.625.6413.21.26Barrier bucket
4/23/049.70E+0149.058.83.110.34.64Barrier bucket
4/21/047.50E+0140.752.9
4/24/048.70E+0151.066.35.4
4/26/041.26E+0264.083.26
4/27/041.23E+0254.164.93105.33Before instability
4/30/041.17E+0250.060.03.110.34.74.2Barrier bucket
4/30/041.30E+0258.169.6310.25.73.6
5/3/041.45E+0263.876.53.210.65.854.3
5/28/044.33E+0116.319.72.58.41.855
6/9/046.70E+0130.837.23.311.12.65before mining for mixed mode
6/29/047.78E+0123.428.43.210.925Barrier bucket, before mining, after linear rf
7/6/047.50E+0123.028.03.411.61.85Barrier bucket, before mining, after linear rf
7/16/049.10E+0129.135.33.511.72.265Barrier bucket, before mining, after linear rf
7/20/046.04E+0122.327.23.310.81.825.4Barrier bucket, before mining, after linear rf
7/20/04626234.5
7/21/04505023.1
8/5/04424220.9
8/11/04303018.8
8/12/04404020.3
From This Time on we started
12/29/046.62E+0118.928.02.9101.85Barrier bucket, before mining, after linear rf
1/7/052.63E+0111.113.83.310.90.774.2Barrier bucket, before mining, after linear rf
1/10/054.23E+0114.717.72.68.61.574Barrier bucket, before mining, after linear rf
1/11/053.11E+0111.614.53.411.30.775Barrier bucket, before mining, after linear rf
1/15/05331414
1/17/058.57E+0125.931.32.99.72.545.3Barrier bucket, before mining, after linear rf
1/18/059.02E+0131.738.22.99.73.154Barrier bucket, before mining, after linear rf
1/25/055.40E+0118.322.02.79.31.94.3Barrier bucket, before mining, after linear rf
1/27/054016.0
1/26/054.04E+0112.416.24.2140.454.5Barrier bucket, before mining, after linear rf
1/28/055.61E+0118.022.13.511.91.294.1Barrier bucket, before mining, after linear rf
1/29/057.79E+0125.030.63.612.31.834.4Barrier bucket, before mining, after linear rf
1/31/057.01E+0122.427.33.411.51.754Barrier bucket, before mining, after linear rf
2/1/056.72E+0121.626.231024.2Barrier bucket, before mining, after linear rf
2/3/057.45E+0124.429.63.3511.11.974Barrier bucket, before mining, after linear rf
2/5/055.81E+0122.827.93.4411.51.763.3Barrier bucket, before mining, after linear rf
2/6/054.34E+0116.219.62.79.141.6663.7Barrier bucket, before mining, after linear rf
2/8/058.93E+0134.241.63.7612.42.464.5
TDR2.60E+0254.070.25538.547.75
6.50E+0254.070.25538.5125
1.80E+0254.070.25538.536.855
2.00E+016.07.85.854.0954.095
2.00E+010.00.0000
0.00E+000.0
1.80E+0296.0
6/30/047932
7/6/047728
7/16/049235.3
12/23/044120.9
12/29/046628
1/10/054220
1/12/054722
1/17/058536
1/18/059040
1/20/059143
1/24/055422.1
1/28/055627
1/30/057829
2/1/056726
2/3/057428
2/8/058941
2/13/053719
2/13/053718
2/17/0545
2/17/054522
2/22/054932
2/22/054932
2/23/059148
2/23/059144
2/24/057236
2/26/057130
2/26/057129
2/27/056939
2/27/057038
3/4/057135
3/4/057135
3/5/058640
3/5/058640
3/7/058140
3/7/058140
3/8/056837
3/9/05168.5
3/10/055728
3/12/0548
3/14/0578
3/15/056430
3/17/058543
3/18/059248
3/20/059847
3/21/059148
3/25/054323
3/26/057641
3/27/056530
3/29/057033
3/30/056328Started using ibs to help cool
4/2/055628
4/4/05124.147
4/7/05113.046.0
4/8/05166.059.3
4/10/0551.025.0
4/14/0574.031.0
4/17/0558.027.0
18-Apr39.019.0
4/20/05108.040.0
4/23/0560.028.0
4/24/05116.054.0
4/25/0590.035.0
4/27/05138.052.0
4/29/05124.045.0
4/30/05121.045.0
5/2/05143.052.0
5/4/05144.051.0
5/7/0544.020.0
5/9/0566.028.0
5/12/05138.051.0
5/13/0594.037.0
5/17/0556.022.0
5/18/0569.026.0
5/19/0558.024.0
5/19/0514.09.0
5/21/0516.010.0
5/23/0559.025.0
5/23/057.06.3
5/24/0533.014.0
5/26/0532.013.0
5/27/0542.018.0
5/28/0545.020.0
5/29/0549.024.0
5/31/0547.021.0
6/2/0565.028.0
6/4/0552.025.0
6/6/05128.051.0
6/7/0585.032.0
6/8/0551.035
6/10/0559.031.0
6/11/0574.030.0
6/17/0543.020.0
6/18/0571.030.0
6/19/0595.042.0
6/20/0530.014.0
6/22/0590.041.0
6/23/0532.014.0
6/24/0562.024.0
6/26/05106.045.0
6/28/0583.033.0
7/1/0553.023.0
7/5/05100.040.0
7/23/0581.026.0
7/26/0558.041.0
7/30/0561.025.0
7/31/0560.026.0
8/2/0594.041.0
8/7/05109.040.0
8/16/0551.025.0
8/18/0546.022.0
8/22/0592.044.0
8/26/05137.078.0
8/27/05116.078.5
8/29/05111.076.0
Ecooling
7/16/0559.515.9
7/18/0590.727.0
7/19/0530.68.5
7/21/0585.028.0
7/22/0548.019.0
7/25/05100.028.0
7/28/0560.020.0
8/1/05100.034.0
8/4/05143.051.0
8/6/05126.040.0
8/8/0559.018.0
8/10/0559.018.0
8/12/0589.024.0
8/13/0585.024.0
8/14/0592.028.0
8/18/0581.025.0
8/19/0597.035.0
8/23/05116.035.0
8/24/05112.031.0
8/26/05137.054.0
8/30/05111.037.0
9/1/05182.062.0
9/2/0546.018.0
9/3/0541.016.0
9/5/0598.030.0
9/6/05110.522.9
9/8/05143.036.0
9/9/0560.016.0
9/12/05109.028.0
9/13/0564.021.0
9/14/0570.021.0
9/16/05136.051.0
9/17/0570.027.0
9/18/05113.027.0
9/20/05165.067.0
9/22/05129.050.0
9/22/05134.047.5
9/24/05141.055.0
9/25/05142.049.0
9/26/05216.064.0
9/28/05241.065.0
9/28/0590.035.0
9/30/0555.020.0
10/1/0569.023.0
10/2/0577.028.0
10/4/05225.062.0
10/5/05280.060.0
10/8/05235.065.0
10/10/05257.066.0
10/12/05183.078.0
10/13/05153.051.0
10/15/05209.065.0
10/15/05117.032.0
10/16/05197.066.0
10/17/05228.066.0
10/19/05111.035.0
10/21/05168.057.0
10/22/05191.068.0
10/23/05219.657.0
10/25/05223.067.0
10/27/05285.067.0
10/29/05247.078.0
10/28/05266.066.0
10/31/05320.072.0
11/2/05220.071.0
11/3/05256.080.0
11/4/0589.045.0
11/5/05171.051.0
11/6/05248.065.0
11/7/05204.070.0
11/9/05200.070.0
11/10/05300.068.0
11/12/05248.065.0
11/13/05252.067.0
11/15/05174.055.0
12/12/0599.040.0
12/13/05132.060.0
12/14/0577.035.0
12/16/05181.058.0
12/17/0572.037.0
12/18/0555.028.0
12/19/05163.065.0
12/21/05219.063.0
12/22/05288.066.0
12/23/05236.064.0
12/25/05137.040.0
12/27/05270.065.0
12/28/05255.059.0
12/30/05273.065.0
1/2/06260.067.0
1/6/06354.072.0
1/7/06326.076.0
1/8/06323.070.0
1/10/06289.766.0
1/11/06284.068.0
1/14/06198.055.0
1/19/06154.061.0
1/23/06115.069.0
1/27/06127.074.0
1/28/06182.069.0
1/30/0630.049.0
2/2/06107.041.0
2/3/06176.041.0
2/4/06201.061.0
2/5/06139.040.0
2/6/06209.059.0
2/7/06181.090.0
2/9/06334.075.0
2/10/06258.055.0
2/12/06258.067.0
2/14/06418.066.0
2/17/06197.066.0
2/18/06131.054.0
2/19/06150.055.0
2/20/06283.058.0
2/21/06166.054.0
2/22/06243.059.0
2/1/06274.062.0
2/1/06240.043.0
Damper Test
8/23/0558.09.8
8/24/05112.024.0
now110.522.9
2.2222222222
7.5
data
00000
00000
00000
00000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
000
000
000
000
00
00
00
00
00
00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Cons data
Pbar intensity, xE10
Long emittance (95%), eV-s
Recycler's best long. emittance as of 04/10/05
Plot
000000
000000
000000
000000
0000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Pink Line
Post IBS Cooling (3/05 - 8/05)
blue Line
Ecool (7/05 - present)
'Feb/04 - Dec/04'
Last 5 to Tev
Pbar intensity, xE10
Long emittance (95%), eV-s
Recycler's Long. Emittance with Electron Cooling
Sheet3
000
000
000
000
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
blue Line
Pink Line
'Feb/04 - Dec/04'
Pbar intensity, xE10
Long emittance (95%), eV-s
Recycler's Long. Emittance Pre IBS Cooling
0000000
0000000
0000000
0000000
00000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
000
000
000
000
000
000
000
000
000
000
00
00
00
00
00
00
00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Pink Line
blue Line
Ecool (7/05 - present)
last 5
dec '05
Jan '06
Feb '06
Pbar intensity, xE10
Long emittance (95%), eV-s
Recycler's Long. Emittance as of 2/28/06
0000
0000
0000
0000
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Pink Line
Post IBS Cooling (3/05 - 8/05)
blue Line
'Feb/04 - Dec/04'
Pbar intensity, xE10
Long emittance (95%), eV-s
Recycler's Long. Emittance Post IBS Cooling
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Mixed Mode Operations
EcoolImplementation
Recycler OnlyShots
Number of antiprotons (x 1010)
Long emittance
14
63
21
50.9913654065
31.908509866
7.0404649281
11.2891480685
48.9543515619
40.7
51
64
54.1471258502
50
49.9728362532
58.0912629581
63.8191827374
16.3045085162
30.7541904285
20.6061774981
7
-
Conclusion (I)Fermilab has a unique operational electron cooling system for cooling of 8.9 GeV/c antiprotonsSince the end of August 2005, electron cooling is being used on (almost) every Tevatron shotIncreases of stash sizes are a direct consequence of the ability to cool the beam efficientlyElectron cooling allowed for the latest advances in the TeV peak luminosityEmittance growth during the mining process has been almost completely eliminated by changing our operating point (tune space)Theoretical model predictionMore tune space investigations in the near futureLifetime degradation is mitigated by a progressive cooling procedureFocus of upcoming studies
Lionel PROST, et al.
-
Conclusion (II)Cooling force has been measured and compared to a non-magnetized modelReasonable agreement with expectationsUncertainties in the electron beam properties make this agreement no better than within a factor of 2-3
Lionel PROST, et al.
-
People of EcoolRecycler department head:Paul DerwentRecycler deputy department head:Cons Gattuso*Ecool Safety officer:Mike GerardiRecycler department personnel:Valeri BalbekovDan Broemmelsiek*Alexey BurovKermit CarlsonJim CrispMartin Hu*Dave NeufferBill Ng Lionel Prost*Stan Pruss*Recycler department personnel (cont):Sasha Shemyakin (GL)*Mary Sutherland*Arden Warner*Meiqin XioOther AD departments:Brian ChasePaul JoiremanRon KellettBrian KramperValeri LebedevMike McGeeSergei NagaitsevJerry NelsonGreg SaewertChuck SchmidtAlexei SemenovSergey SeletskiyJeff SimmonsKarl Williams* Main experimentalists (experimental studies, data analyses,); Primary ecool theorist (theoretical analyses); Primary technical support (tech support coordination,)
Lionel PROST, et al.
-
EXTRAS
Lionel PROST, et al.
-
Setup of Fermilabs Electron Cooler
Lionel PROST, et al.
-
Electron beam parameters (for cooling)Electron kinetic energy 4.34 MeV Uncertainty in electron beam energy 0.3 %Energy ripple250 V rmsBeam current 0.1 A DCDuty factor (averaged over 8 h)>95 %Electron angles in the cooling section(averaged over time, beam cross section, and cooling section length), rms 0.2 mrad
Lionel PROST, et al.
-
Simplified electrical schematic of the electron beam recirculation systemBeam power 2.15 MWCurrent loss power 21.5 WPower dissipated in collector 1.6 kWFor I= 0.5 A, I= 5 A:The beam power of 2 MW requires the energy recovery (recirculation) scheme
Lionel PROST, et al.
s
C
u
r
r
e
n
t
C
o
n
t
r
o
l
E
l
e
c
t
r
o
d
e
E
l
e
c
t
r
o
n
B
e
a
m
+
4
.
3
M
V
A
n
o
d
e
P
S
H
i
g
h
V
o
l
t
a
g
e
P
e
l
l
e
t
r
o
n
T
e
r
m
i
n
a
l
+
3
k
V
C
o
l
l
e
c
t
o
r
S
u
p
p
r
e
s
s
o
r
E
l
e
c
t
r
o
d
e
+
C
a
t
h
o
d
e
A
n
o
d
e
L
o
s
20 kV
Ra
-
Electrostatic generator: the Pelletron (developed by NEC)Improved Van de Graaff generatorCharge carried by a chain (metal cylinders joined by nylon links) instead of a rubber beltInduction system to charge the chain (instead of rubbing contacts or corona discharges)
Lionel PROST, et al.
-
Preview of whats inside the pressure vesselHigh-voltage column with grading hoops partially removed to show the accelerating tube (right) and the charging chains (far center).
Lionel PROST, et al.
-
DiagnosticsYAG crystal, OTR monitors throughout the beam lineBeam size (shape), distributionUsed to compare to optics models
1 multi-wire scannerBeam size and shape after 180 bend
Removable apertures in the cooling sectionBetween each of the ten cooling section solenoidBeam size and angle
BPMsBetween each of the ten cooling section solenoid + 16 in other beam lines (accel, supply, return, transfer, decel)Can measure both pulsed and DC beam Capable of monitoring both electrons AND pbars
Lionel PROST, et al.
-
OTR Detectors for the Medium Energy Electron Cooler Detector characteristics5 m foilLower current limit 20mAResolution 50 m
ApplicationsReal-time charge density distribution and beam size measurementsMeasurement of beam initial conditions in the acceleration sectionBeam ellipticity measurementsBeam temperature measurements with pepper-pot
Beam Image from OTR at full current (acceleration tube exit)Beam profile versus Lens current on acceleration side
Lionel PROST, et al.
-
Neighborhood with the Main Injector
Magnetic fields of busses and MI magnets in the time of ramping causes an extensive motion of the electron beam (up to 0.2 mm in the cooling section and up to 2 mm in the return line)
MI radiation losses sometimes result in false trips of the ECool protection systemElectron beam motion and MI losses at R04 location in the time of MI ramping. 0.55 Hz oscillation is due to 250 V (rms) energy ripple.2 secMI bus currentMI lossXY1mm
Lionel PROST, et al.
-
Low magnetic field in the cooling sectionCooling is not magnetized
The role of the magnetic field in the cooling section is to preserve low electron angles,
A typical length of B perturbation, ~20 cm, is much shorter than the electron Larmor length, 10 m. Electron angles are sensitive to , not to B .Transverse magnetic field map after compensation (Bz = 105 G).Simulated angle of an 4.34 MeV electron in this field. RMS angle is < 40 rad.
Lionel PROST, et al.
-
Beam size measurements in the Cooling Section11 movable orifices (not in phase) in the cooling sectionThe scrapers are diaphragms of 15 mm diameter, located every 2 m. While only one of them is in place, the beam is shifted in some direction until it touches the scraper. The bpm data for the beam center is taken at this point. The beam is shifted in other direction, and the center coordinates at touch are detected again; usually 8 directions are used. Then, the entire procedure is repeated for other scrapers. From these data, the beam ellipse and the scraper offsets are found for every scraper involved.Initial conditions for the beam envelope are fitted for these ellipses. A cylindrical boundary might not guarantee low angles in the middle of the beam because of aberrations radial angletangential angledensity
Lionel PROST, et al.
- Scraper Measurements Dec 1 (nominal settings, 500 mA)SCC00SCC70SCC60SCC50SCC40SCC30SCC20SCC10SCQ01SCC90SCC80Beam radius ~ 4.5 mmAveraged rms angle
-
Comparison of two focusing settings Envelope (fit) along the scrapers 0-5One lens changed by 2 AAverage rms envelope angle is 0.5 mradNominalAverage rms envelope angle is 0.2 mrad
Lionel PROST, et al.
-
Why sudden new interest in high energy cooling?The existing stochastic cooling technology is band-width limited (10 GHz or so).The lack of progress in bunched-beam stochastic coolingThe advance in electron gun and collector technology (experience of low energy e-cooling), and in recirculation of DC beams.The advance in recirculating linac technologies.The advance in linear optics on beams with a large angular momentum.
Lionel PROST, et al.
-
Simulation of cooling demonstrationWithout cooling -- the momentum distribution remains flat over 0.3% span for 30 minutesCoasting beam, IBS+ECOOL simulation, n = 2 mm mrad, Ie=0.1 A, rms angular spread = 0.5 mrad
Lionel PROST, et al.
-
Recycler measured momentum distribution using Schottky1.5e11 pbars, n = 2 mm mradMomentum acceptance (flat central part): about 0.5% (+/- 22 MeV/c)
Lionel PROST, et al.
-
Drag rate as a function of the electron beam current3.67 MeV/c momentum deviation, on axis, nominal cooling settingsThe drag force is nearly constant at 0.1 0.5 A, while in simulations the current density at the axis is twice higher at 0.5 A than at 0.1 A. Not a real fitDrag force on axis appears to be independent of the electron beam current Quite consistent with equilibrium longitudinal emittance measurements
Lionel PROST, et al.
-
Drag rate as a function of the transverse emittance1.84 and 3.67 MeV/c momentum offsets, 100 - 500 mA e-beam, on axisScattered in the data likely dominated by the difficulties in getting similar machine conditions
Lionel PROST, et al.
-
Emittance growth during mininge-beam: 500 mA, +3.5 mm offsetpbars: 180e10e-beam: 500 mA, +3 mm offsetpbars: 180e10 Stochastic cooling system was turned off when mining, e-beam (when used) remained onDampers are on for all measurementspbars: 114e10 Initial rate: 17 p mm mrad/hourInstrumentation problem
Lionel PROST, et al.
-
Emittance growth during mining reduced by ~10Changed working point for the tunes (in order to split them more), from 0.414/0.418 (H/V) to 0.453/0.473 (H/V)Electron beam currentHorizontal emittanceElectron beam positionLongitudinal emittance (circle)Vertical emittance (circle)Pbar intensity (circle)Stochastic cooling system is turned off before mining~2 p mm mrad/hourPhase density when mining = 0.9Mining227e10100 mA
Lionel PROST, et al.
-
Correlation with presence of electron beam & cooling ?40 minutes of electron cooling on axis at 300 mALifetime drops and recovers ~1 hour laterBut phase density has increased by ~2 !Pbar intensity (1 1010/div)Longitudinal emittance (20 eV s/div)Vertical emittance (2 p mm mrad/div)Electron beam current (0.1 A/div)
Lifetime (1 hour running average) [circle](500 h/div)3.8 p mm mrad68 eV s158 10100 h2000 h
Lionel PROST, et al.
-
Comparison with cooling force measured at low-energy coolersComparison with data for normalized longitudinal cooling force measured at low energy coolers adapted from I.N. Meshkov, Phys. Part. Nucl., 25 (6), p. 631 (1994).
Red triangles represent Fermilabs data measured at 0.1 A. The current density is estimated in the model with secondary electrons.
Lionel PROST, et al.