Electron Cooling Commissioning Update Run II meeting May 12, 2005 L. Prost, Ecool Group

Electron Cooling Commissioning Update 2 Outline  Goal, design, plan, installation highlights…  Commissioning progress highlights  Some specifics of what has been achieved  What’s ahead, some important issues that remain  Conclusion

Electron Cooling Commissioning Update 3 People of Ecool  Recycler department head:  Sergei Nagaitsev  Recycler deputy department head:  Cons Gattuso  Ecool Project engineer:  Jerry Leibfritz  Ecool Safety officer:  Mike Gerardi  Electron cooling group:  Alexey Burov  Kermit Carlson  Grigory Kazakevich  Tom Kroc  Lionel Prost  Sasha Shemyakin (GL)  Mary Sutherland  Vitali Tupikov  Arden Warner  Recycler department personnel:  Valeri Balbekov  Dan Broemmelsiek  Jim Crisp  Martin Hu  Dave Johnson  Dave Neuffer  Bill Ng  Stan Pruss  Meiqin Xio  Other AD departments:  Brian Chase  Paul Joireman  Ron Kellett  Brian Kramper  Valeri Lebedev  Mike McGee  Jerry Nelson  Lucy Nobrega  Greg Saewert  Chuck Schmidt  Alexei Semenov  Sergey Seletskiy  Karl Williams

Electron Cooling Commissioning Update 4 Electron Cooling: Long. Rate Design Goal  Cooling needed: 30 eV-s per hour  To minimize the IBS rate, a 65-eV-s stack will be kept in a 4-μs long bunch; 95% of particles will have its energy offset ≤8 MeV.  For particles with ΔE ≈ 8 MeV the drag rate needs to be about 4 MeV/hr to cool 15 eV-s in 30 minutes.

Electron Cooling Commissioning Update 5 Performance goal for the long. equilibrium emittance: 54 eV-s

Electron Cooling Commissioning Update 6 Electron beam design parameters  Electron kinetic energy 4.34 MeV  Absolute precision of energy  0.3 %  Energy ripple500 V rms  Beam current 0.5 A DC  Duty 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

Electron Cooling Commissioning Update 7 Commissioning challenge  Technical issues not fully resolved with prototype system at Wide Band  Poor reliability of operation at 4.3 MV  Insufficient quality of the cooling section magnetic field  High beam losses  Low-frequency electron beam motion  Inadequate protection system  Concurrently attain stable operation at 4.3 MV, 0.5 A with rms angular spread < 0.2 mrad in cooling section

Electron Cooling Commissioning Update 8 Commissioning guiding principles  Establish ‘some’ beam and verify optics (pulsed beam, first order)  Choice of a pulsed beam over low-current DC beam  Check polarities, calibration,… of all lenses and correctors  Increase beam intensity (pulsed → DC)  Low current loss to maintain recirculation  Make the beam cold (i.e. good understanding of the optics and beam control)  Only way to achieve cooling  Maintain hardware integrity (i.e. avoid drilling a hole !)  U-Bend mode to develop and test protection systems

Electron Cooling Commissioning Update 9 The commissioning project plan summary  On Feb 1, 2005 the Recycler starts to contribute to HEP luminosity (mixed-source operations).  This continues uninterrupted until about Apr 1,  On Feb 1, 2005 the effort switches over to the electron beam commissioning.  Pelletron and U-bend start-up  On Mar 15, 2005 start commissioning of the complete electron beamline.  Run electron beam in a pulsed mode  Pbar operations are uninterrupted  On Apr 4, 2005 start establishing a DC beam.  The Recycler beam may be interrupted  Investigate and correct MI ramp effects on the electron beam  Minimize the effects of the electron beam on the Recycler beam, start running pbar and electron beams concurrently  Establish a 500-mA dc electron beam by July 08, 2005

Electron Cooling Commissioning Update 10 The commissioning project plan summary (cont’)  On July 11, 2005 start adjusting the electron beam parameters  500 mA dc beam is stable  Establish and adjust the beam trajectory in the cooling section  Measure the electron beam properties  The pbar beam is interrupted when electron envelope is measured.  By Sep 08, 2005 demonstrate the electron cooling  In Sep-Dec 2005 the Recycler continues to operate and contribute to the HEP luminosity.  The cooling rates are measured; electron cooling is optimized  Dec 31, 2005 – project ends. Plan assumed no major component failures and no lab wide shutdown in ‘05

Electron Cooling Commissioning Update 11 Major changes to the plan (so far)  Commissioning began ~1 month late  Increased number of shifts/week to compensate  Should not affect milestone for first observation of electron cooling of pbar  U-bend and full line are being commissioned in parallel  Partly because of late start of commissioning  Partly because of delays in getting DC beam permit  Higher number of shifts allows simultaneous progress

Electron Cooling Commissioning Update 12 Electron Cooling Installation Schedule/Highlights  5/04 – MI-31 Building Construction Complete  5/04 – R&D Operations at Wide Band Complete  6/04 – Disassembly/Move of Pelletron Begins  8/04 – 13-week Lab Wide Shutdown Begins (Pelletron Assembly Suspended)  In situ magnetic field measurements of the cooling section solenoids  11/04 – Lab Wide Shutdown Complete (Pelletron Assembly Resumes)  2/05 – Pelletron/E-Cool Installation Complete  3/05 – Commissioning Begins

Electron Cooling Commissioning Update 13 Electron cooling system setup at MI-30/31 Added section (includes additional pumping) Beam line accommodates both U- bend and vertical bend magnets Fast acting valves Magnetically shielded to protect e beam from fields imposed by the MI bus

Electron Cooling Commissioning Update 14 Electron cooling system setup at MI-30/31 Pelletron (MI-31 building) Cooling section solenoids (MI-30 straight section)

Electron Cooling Commissioning Update 15 Mechanical oscillations of the Pelletron  Mechanical vibrations in the Pelletron were greatly reduced between the Wide Band assembly and the current assembly at MI-31  May help reduce beam motion in accel/deccel tubes  May help HV stability (i.e. avoid full discharges) MI-31 assembly Wide Band lab assembly ~ 3 Hz: Chain transverse oscillations ~ 30 Hz: Rotating shaft

Electron Cooling Commissioning Update 16 Commissioning Milestones Highlights  Feb, 21 st – All vacuum work Complete  Feb, 22 nd – First HV on terminal  Feb, 25 th – Installation Complete  Mar, 2 nd – Stable 500 kV in air  Pulsed beam to first BPM  Mar, 7 th – All systems ready for commissioning  Charging system, gun, pulser work  Mar, 8 th – Stable 2.5 MV (tank pressurized w/ SF6) – Begin tubes conditioning  Mar, 10 th – First light on OTR (acceleration side)  Mar, 12 th – End of tubes conditioning (5 MV stable)  Mar, 17 th – 4.3 MeV, 0.5 A pulsed beam to collector (U- Bend mode, low losses)  Regulation system works properly  Mar, 21 st – Correctors to compensate dipole effects of Ecool on Recycler optics commissioned

Electron Cooling Commissioning Update 17 Commissioning Milestones Highlights (cont’)  Mar, 27 th – 4.3 MeV, 50 mA pulsed beam through cooling section  Correctors settings very different from calculations based on magnetic measurements  Mar, 28 th – Apr, 5 th : Shutdown (Pelletron tank opened)  Charging circuitry fixed  Updated gun lens power supply  Removed hard-wired -5 kV: Ready for DC beam  Apr, 7 th – 4.3 MeV, 35 mA DC beam to collector (U- Bend mode)  Apr, 12 th – Low intensity, 4.3 MeV pulsed beam to collector (full line)  Protection systems commissioned with pulsed beam  Apr, 20 th – First DC beam (few mA) in Recycler beam line  Apr, 27 th – 4.3 MeV, 350 mA pulsed beam to collector (full line)  Correctors settings based on magnetic measurements

Electron Cooling Commissioning Update 18 Commissioning Milestones Highlights (cont’)  May 3 rd – 4.5 MeV, 750 mA DC beam to collector (U- Bend)  Low magnetic flux configuration  Preparation for ‘long run’…  … but full discharge occurrences increase  May 4 th – First beam size measurements in cooling section (pulsed beam)  Recycler empty

Electron Cooling Commissioning Update 19 Tubes conditioning  Pelletron is divided into 6 sections  Each section was conditioned to 1.2 MV  All sections together were conditioned to 5 MV (the operation voltage is 4.32 MV)  Conditioning took 5 days (elapsed time)  Detail for individual sections:  Other info:  First vacuum activity began at 0.55 – 0.75 MV for individual sections  A Java Final State Machine was used for conditioning  Conditioning was interrupted several times for some beam related studies at low energy

Electron Cooling Commissioning Update 20 Tubes conditioning - Sections 1-3 (example)

Electron Cooling Commissioning Update 21 High Voltage Stability  Reliable operation at 4.3 MV  Partly due to added section  Wide Band vs MI-31 Pulsed beam, 3 hours: Multiple discharges Pulsed and DC beam, 6 hours: No discharge Intentional Pulsed beam

Electron Cooling Commissioning Update 22 Protection system  Fast acting valves between Pelletron and Recycler ring (on Supply and Return lines)  Activated if pressure rises on the Pelletron side (as a result of a full discharge for instance)  Monitor several dozen signals with the Pelleron Mode Controller (Java Application)  Signals include: - All BLMs - Capacitive pickups (CPOs) (e.g.: for terminal voltage discharges)  When one channel is ‘out of tolerance’ - Gun is closed (i.e. beam extraction is interrupted) - Trip flag is up (need operator to reset before re-establishing beam) - All signal waveforms are saved in the buffer (512 ms long over a time window that includes the trip)  Both the Fast acting valves’ logic and the Pelletron Mode Controller were tested  Improvements were made (increase response speed, more devices recorded, adjusted limits,…)

Electron Cooling Commissioning Update 23 Protection system (cont’)  To avoid full discharges and/or damaging the tubes, it is important to shut off the gun as fast as possible  Right now, it takes about ~1 ms to close the gun after the beam permit has been taken off  Faster circuit will be installed during next shutdown Yellow: Fast CPO Cyan: Beam permit White: Cathode current transformer ~1 ms Gun closes Permit removed

Electron Cooling Commissioning Update 24 Diagnostics  YAG crystal, OTR monitors throughout the beam line  Beam size (shape), distribution  Used to compare to optics models  1 multi-wire scanner  Beam size and shape after 180° bend  Removable apertures in the cooling section  Between each of the ten cooling section solenoid  Beam size and angle  BPMs  Between 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

Arden Warner, AD/Recycler/Electron Cooling OTR Detectors for the Medium Energy Electron Cooler  Detector characteristics  5 µm foil  Lower current limit 20mA  Resolution 50 µm  Applications  Real-time charge density distribution and beam size measurements  Measurement of beam initial conditions in the acceleration section  Beam ellipticity measurements  Beam temperature measurements with pepper-pot Beam Image from OTR at full current (acceleration tube exit) Beam profile versus Lens current on acceleration side

Electron Cooling Commissioning Update 26 Recirculation in U-Bend mode – Short run  700 mA DC beam re-circulating with low losses (5-10 minutes without discharges) Green: Bias current Cyan: Collector pressure Blue: Acceleration tube current Red: Needle current Relative current loss at 0.5 A: ~6e -6

Electron Cooling Commissioning Update 27 Beam in cooling section (i.e. in Recycler ring)  Pulsed beam transported through the full line with low loss and low ‘spatial oscillations’ in cooling section  Correctors settings in cooling section based on magnetic measurements made in-situ during installation Cooling section Horizontal displacement Vertical displacement BPM intensities (correspond to ~50 mA)

Electron Cooling Commissioning Update 28 Optics measurements  Understanding the beam line’s optics (supply line in particular) is primordial in order to gain the beam envelope control necessary to achieve cooling  Principle: Differential trajectories measurements (good for linear optics only)  Method: - Take reference orbit - Apply kick and measure betatron motion of the beam - Repeat 4 times (+ ‘energy kick’ for dispersion) - Check reference orbit  Preliminary measurements:  Determine that all lenses and correctors are hooked up correctly and/or identify problems  Exercise/commission differential orbit measurement programs  Calibration of power supplies  Help achieving clean transport of the beam

Electron Cooling Commissioning Update 29 Supply line optics: Data vs OptiM  After various problems were found and fixed, and several iterations for calibration purposes, measurements (with pulsed beam) are mostly consistent with OptiM calculations Supply line

Electron Cooling Commissioning Update 30 Preliminary energy measurements  For cooling, the electron beam and pbar bunches energies need to be ‘aligned’, thus measuring the electron beam absolute energy is critical (<0.3 %)  Principle: Measure the Larmor frequency of the beam oscillations in the cooling section solenoid (via differential trajectories measurements)  So far, measurements indicate that the energy is lower than expected by ~3%  Correlated by ‘optimum’ bends settings found  Awaits more precise measurements with DC beam

Electron Cooling Commissioning Update 31 Preliminary total angles  Except for dipole offsets, no attempts were made to minimize the angles (at this stage)

Electron Cooling Commissioning Update 32  DC beam commissioning in the full line  Beam line optics Needs to be analyzed and adjusted to establish design beam size and rms angular spread  Energy stability Energy fluctuation is estimated by analysis of a BPM signal from a high- dispersion region  Establish 0.5 A DC beam  Observe electron cooling  The energies are aligned within 0.3 %  Effect of electron cooling is observed by longitudinal Schottky monitor What’s next ?

Electron Cooling Commissioning Update 33 Interference with the Recycler’s work for luminosity  Effects of ECool bends and cooling section field on the pbar dynamics in RR- Corrected and tested  Effects of the e–beam space charge on pbar dynamics in RR- supposed to be negligible  Changes in the pbar lifetime caused by a pressure rise in the cooling section- is negligible according to measurements in WB. Also, fast isolation valves installed and tested  Drag force- many e- beam measurements can be done either at low electron currents or at the electron energy shifted by 1%  Measurements of DC beam dimensions in CS and measurements with the YAG/OTR downstream of the cooling section- no pbars in RR  If above is correct, the electron cooling tune-up may be done with Recycler being emptied between the TeV shots and pbar shots from the Accumulator

Electron Cooling Commissioning Update 34 Some Remaining Outstanding Issues  Recirculation for long runs (i.e. hours) is not established  Full discharges cannot be prevented (so far)  Main injector beam loss trips our loss monitors  Temporary fix: increase protection system limits but…  … beat the purpose  Need MI people to work on reducing losses and/or additional shielding  OTR cameras in MI-30 tunnel damaged by radiation  Beam motion with MI ramps  Prevents recirculation high intensity beam  Additional magnetic shielding will be installed

Electron Cooling Commissioning Update 35 MI losses (mostly detected on the return line)  Losses appear to be related to slip stacking  First attempts to reduce them were not successful Green: C90 loss monitor Red: R06 loss monitor Blue: R04 loss monitor Cyan: MI beam current Original trip level for DC beam operation

Electron Cooling Commissioning Update 36 MI ramp induced beam motion  Stray fields from the MI bus and/or QCL alter the beam orbit in the return line (mostly)  Induces losses downstream Beam loss spikes on the QCL negative slope 1 Hz repetition rate (random w.r.t. MI ramp)

Electron Cooling Commissioning Update 37 Summary  Achieved stable high voltage regulation (with beam) at designed Pelletron energy (4.3 MV)  Achieved DC electron beam in the Recycler beam line (35 mA)  Achieved ‘stable’ (i.e. minutes) high intensity (i.e. 750 mA) DC beam in U-Bend mode  Implemented and tested (in U-Bend mode) all protection systems  Interference with Recycler operation was minimal  Will increase now  Although the commissioning started later than originally planned, we still expect to observe cooling of pbar by September 8, 2005.