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

Electron Cooling Commissioning UpdateElectron Cooling Commissioning Update

Run II meetingMay 12, 2005

L. Prost, Ecool Group

Electron Cooling Commissioning Update 2

OutlineOutline

Goal, design, plan, installation highlights… Commissioning progress highlights Some specifics of what has been achieved What’s ahead, some important issues that

remain Conclusion


People of EcoolPeople 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: Long. Rate Design GoalElectron 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.


Performance goal for the long. equilibrium emittance: 54 Performance goal for the long. equilibrium emittance: 54 eV-seV-s

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Pbar intensity, xE10

Lo

ng

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-s Recycler (measured)

Accumulator (measured)

Ecool performance goal


Electron beam design parametersElectron beam design parameters

Electron kinetic energy 4.34 MeV Absolute precision of energy 0.3 % Energy ripple 500 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


Commissioning challengeCommissioning 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


Commissioning guiding principlesCommissioning 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


The commissioning project The commissioning project planplan summary summary

On Feb 1, 2005 the Recycler starts to contribute to HEP luminosity (mixed-source operations). This continues uninterrupted until about Apr 1, 2005.

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


The commissioning project The commissioning project planplan summary (cont’) 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


Major changes to the plan (so far)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 Installation Schedule/HighlightsElectron 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 system setup at MI-30/31Electron 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 system setup at MI-30/31Electron cooling system setup at MI-30/31

Pelletron(MI-31 building)

Cooling section solenoids

(MI-30 straight section)


Mechanical oscillations of the PelletronMechanical 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)

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MI-31 assemblyWide Band lab assembly

Peak @ ~ 3 Hz: Chain transverse oscillations

Peak @ ~ 30 Hz: Rotating shaft


Commissioning Milestones HighlightsCommissioning Milestones Highlights

Feb, 21st – All vacuum work Complete Feb, 22nd – First HV on terminal Feb, 25th – Installation Complete Mar, 2nd – Stable 500 kV in air

Pulsed beam to first BPM Mar, 7th – All systems ready for commissioning

Charging system, gun, pulser work Mar, 8th – Stable 2.5 MV (tank pressurized w/ SF6) –

Begin tubes conditioning Mar, 10th – First light on OTR (acceleration side) Mar, 12th – End of tubes conditioning (5 MV stable) Mar, 17th – 4.3 MeV, 0.5 A pulsed beam to collector

(U-Bend mode, low losses) Regulation system works properly

Mar, 21st – Correctors to compensate dipole effects of Ecool on Recycler optics commissioned


Commissioning Milestones Highlights (cont’)Commissioning Milestones Highlights (cont’)

Mar, 27th – 4.3 MeV, 50 mA pulsed beam through cooling section Correctors settings very different from calculations

based on magnetic measurements Mar, 28th – Apr, 5th: Shutdown (Pelletron tank

opened) Charging circuitry fixed Updated gun lens power supply Removed hard-wired -5 kV: Ready for DC beam

Apr, 7th – 4.3 MeV, 35 mA DC beam to collector (U-Bend mode)

Apr, 12th – Low intensity, 4.3 MeV pulsed beam to collector (full line) Protection systems commissioned with pulsed beam

Apr, 20th – First DC beam (few mA) in Recycler beam line

Apr, 27th – 4.3 MeV, 350 mA pulsed beam to collector (full line) Correctors settings based on magnetic measurements


Commissioning Milestones Highlights (cont’)Commissioning Milestones Highlights (cont’)

May 3rd – 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 4th – First beam size measurements in cooling section (pulsed beam) Recycler empty


Tubes conditioningTubes 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

Section # 1 2 3 4 5 6 Time, h 8 5 4.5 5 5 8


Tubes conditioning - Sections 1-3 (example)Tubes conditioning - Sections 1-3 (example)


High Voltage StabilityHigh 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


Protection systemProtection 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,…)


Protection system (cont’)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


DiagnosticsDiagnostics

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 OTR Detectors for the Medium Energy Electron Cooler 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-pot100 200 300 400 500 600

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B: SPA06=5.8 A D: SPA06=9.8 A F: SPA06=11.8 A H: SPA06=13.8 A J: SPA06=15.8 A L: SPA06=17.8 A N: SPA06=19.8 A

Beam Image from OTR at full current (acceleration tube exit)

Beam profile versus Lens current on acceleration side


Recirculation in U-Bend mode – Short runRecirculation 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


Beam in cooling section (i.e. in Recycler ring)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)


Optics measurementsOptics 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


Supply line optics: Data vs OptiMSupply 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

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Preliminary energy measurementsPreliminary 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


Preliminary total angles Preliminary total angles

Except for dipole offsets, no attempts were made to minimize the angles (at this stage)

Component Upper limit, rad

Measured by Achieved, rad

Temperature 90 Pepper pot + YAG/ OTR

No data

Aberration 90 Pepper pot + YAG/ OTR; BPM responses

No data

Envelope scalloping

100 Movable orifices ~1000 @ 0.4A pulsed

Dipole offsets

100 BPMs ~ 300

Beam motion 50 BPMs ~100 Drift velocity 20 Calculated Total 200 ~ 1000


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 ?What’s next ?


Interference with the Recycler’s work for Interference with the Recycler’s work for luminosityluminosity

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


Some Remaining Outstanding IssuesSome 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


MI losses (mostly detected on the return line)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


MI ramp induced beam motionMI 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)


SummarySummary

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.

Documents

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