Use of Electron Lens in Tevatron and LHC

Use of Electron Lens in Tevatron and LHC Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 1

Beam-beam Compensation with Electron Beam “…to compensate (in average) space charge forces of positively charged protons acting on antiprotons in the Tevatron by interaction with a negative charge of a low energy high-current electron beam ” (1997) Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 2

Compensation with Two TELs Yu. Alexahin a n Tev Run II: 36 x 36 bunches in 3 trains n compensate beam-beam tune shifts Xiaolong Zhang - FNAL a) Run II Goal q b) one TEL q c) two TELs q d) 2 nonlinear TELs b n c q d LHC IR Upgrade Workshop - Oct. 3 -4, 2005 requires q 1 -3 A electron current q stability d. J/J<0. 1% q e-pbar centering q e-beam shaping 3

TEL 1 in Tevatron Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 4

Use of Electron Lens in Tevatron (TEL) n Beam-beam compensation studies Tune shift & beam lifetime vs. electron beam parameters, etc. n DC beam studies DC beam cleaning efficient, DC beam measurement, calibration of the abortgap monitors, etc. n Beam diagnostics tool Pbar tune measure by exciting pbar bunches, controlled proton or pbar remover, noise vs. beam emittance growth, etc. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 5

Beam Tune Shift Three bunches in the Tevatron, the TEL acts on one of them; Tuneshift d. Qhor=+0. 009 Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 6

Tuneshift vs. Electron Current Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 7

Tuneshift vs. e_Beam Timing Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 8

Electron Beam Profile Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 9

“Collimation” Effect Need electron gun with smooth edge. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 10

Beam Lifetime vs. Tune Flat e-beam Xiaolong Zhang - FNAL With d. QTEL~0. 004 Gaussian e-beam LHC IR Upgrade Workshop - Oct. 3 -4, 2005 11

Gaussian Gun n n Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 Beam profile controlled by special electrode Somewhat reduced current density in the center need of higher voltage Beamsize smaller Difficult to align the beams New gun: flat top with smooth edge 12

New Electron Gun Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 13

Beam-beam Compensation Emittance Scallops Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 14

Beam-Beam Compensation Store #2540 May 12, ‘ 03 A 9 : 4. 1 mm mrad/hr A 21 : 2. 2 mm mrad/hr A 33 : 1 mm mrad/hr -TEL on it Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 15

Beam Loss vs. Electron Position ØBeam loss ~1/R 3, R is distance between P/Pbar beam and ebeam. ØNo effect on protons while ebeam acting on Pbar, and vice versa. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 16

Beam Loss vs. Electron Position Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 17

DC Beam Cleaning Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 18

Calibration of the Abort Gap Monitor Calibration of the SL abort gap monitors: AGIGI 1, AGIGI 2, AGIGI 3, and SLPAH[37]. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 19

DC Beam Cleaning • Fire TEL in 3 gaps every 7 • • turns to excite resonance TEL is equivalent to 100 k. W “tickler” Exciting 4/7 th order resonance in vertical. Reduces DC beam intensity. Protect CDF detector by eliminating the proton loss spikes. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 20

Noise vs. Emittance Growth • TEL e-current turn-by-turn noise amplitude d. J_e ~3 -5 m. A p-p while operating for BBC with d. Q > 0. 005 0. 1 -0. 2 /hr • That is less though comparable with “natural” emittance growth of 0. 2 -0. 5 /hr Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 21

Exciting Pbar for Tune Measurment Enable us to measure Pbar tune at the EOS by 21 MHz Schottky System Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 22

P/Pbar Remove p/pbar in a controlled manner to enable the Endof-store single beam study. Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 23

The 2 nd Electron Lens (TEL 2) n n 57 electron beam bend with strength solenoids Upgraded BPMs • TEL 2 under testing at E 4 R • Magnetic fields meet requirement • Will be installed coming shutdown Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 24

Main Difficulties to Overcome Ø Modulator: q q q Ø Ø Short pulse Higher output voltage >7 KV Reliable, stable and no afterpulse BPM: need offset between e-pulse and P/Pbar bunch < 0. 2 mm, now ~1 -1. 5 mm Resolution of bunch-by-bunch tune measurement: <0. 0002 needed, 0. 001~0. 002 achieved; Data acquiring speed: from a few minutes (now) to a few seconds (future). Orbit stabilization Alternating transverse electron beam position for beam-beam compensation and DC beam cleaning Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 25

Using Tevatron Electron Lens for LHC n n The two TELs will be available upon the termination of the Tevatron Electron beam is more flexible than the wire: • • Transverse position can be changed when needed Don’t need to be cooled Don’t pose any aperture limitations Can do both head-on and parasitic beam-beam compensation • Can be used for nonlinear beam-beam compensation • May be used for other purpose (help beam diagnostics; DC beam cleaning; etc. ) § More studies needed on Tevatron Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 26

Summary n n n TEL 1 is running successfully and reliably for Tevatron, and is crucial for daily Run. II operation. We had one successful attempt to use it for beam compensation, despite its main function as DC beam cleaning and limited machine study time. The 2 nd TEL is tested 90% successfully so far and will be installed this coming shutdown. We have plans for the upgrades and bring TEL for beam-beam compensation. More studies are ahead of us… Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 27

Tuneshift vs. e_Beam Position Xiaolong Zhang - FNAL LHC IR Upgrade Workshop - Oct. 3 -4, 2005 28