Interaction Region Vacuum Chamber Upgrades

Interaction RegionInteraction RegionVacuum Chamber UpgradesVacuum Chamber Upgrades

Presented by: Scott DeBarger

Contributors: D. Arnett, B. Bigornia, C. Carr,J. Langton, S. Metcalfe, D. Kharahk, M. Kosovsky,

N. Kurita, R. Pope, N. Reeck, A. Sheng, B. Smith

Interaction Region Vacuum Chamber Upgrades p.2 of 25

OutlineOutline

Forward Q2 Chamber

Q1/Q2 HOM Bellows

HER Q4 & Q5 Vacuum Chambers; HOM Absorbing Bellows

LER Q4 R Temporary Chamber

LER Q4 & Q5 Vacuum Chambers

DS-7 Transition

LER 2062 Chamber

LER 2143 Collimator

Interaction Region HOM Absorbers

Additional Diagnostics

HOM Straight Bellows


Replaced Q2R with a Q2L chamber in 2002 Improve Beam Stay-Clear and reduce HOM

generation (see mask at right) Chamber failed (following operation) due to

material flaw in the GlidCop

Original Q2R chamber reinstalled in 2003 Does not maintain Beam Stay-Clear No evidence that it creates increased HOMs

New Q2R installed March 2006 Opportunistic installation in conjunction with

Q1/Q2 bellows seal Still no effect on HOM generation observed

Forward Q2 ChamberForward Q2 Chamber


Identified as a critical upgrade at previous review Technically very challenging

Limited space available Anticipated high power loads

Design compromises travel during installation to accommodate new HOM absorption arrangement

61 mm maximum tile/slot length Absorbing tiles are open to the convolutions

No additional tile set needed in bellows cavity HER Arc Bellows features

Spring, Stub, RF shield (See M. Sullivan talk)

Q1/Q2 HOM BellowsQ1/Q2 HOM Bellows


Q1/Q2 HOM BellowsQ1/Q2 HOM Bellows

RF Seals replaced 22 February 2006(see M. Sullivan talk)

Installed design

New stub in fabrication

•Materials in hand (AlN-SiC tiles, GlidCop, bellows)•Working aggressively to complete new bellows modules•Hope to install during current shutdown


HER Q4 & Q5 ChambersHER Q4 & Q5 Chambers

HER Q5 & Q4 Chambers General issues

Mechanical & HOM failures in the NEG screens

Beam Stay-Clear (BSC) & Luminosity cone restrictions

Thermal motion of magnets Original Q4 & Q5 are rigid chambers that have minimal to no clearance to their respective

magnets

Global alignment errors between the 10-meter Collimator and Q5 L and between Q5 R and High Power Dump.

History of mask and flange failures due to SR heating

NEG heating during high current operation


Design goals (achieved) LER: 4.5A, HER 2.2 A operation Respect the defined BSC/Luminosity cone and

existing magnet envelopes. Maintained a 2mm gap to poles and a 3mm gap

to coils

Reduce operating thermal gradients Improve kinematics and stabilize BPMs

Added a bellows between Q4, Q5 Added a flex flange between Q2L & Q4L Replaced beampipe supports

Decrease the RF leakage to the pumps Screen hole diameter reduced to

3 mm and depth increased to 6mm


Q5 NEG RF Screen



HER Q5 L Chamber Installed Fall 2005

HER Q4 & Q5 R and HER Q4 L Chambers

Installed beginning in August 2006

Installation revealed vertical misalignment of ~9 mm at HER High Power Dump (corrected)

Q5 L installation

Aluminum clamshell design Profile matched to available space

Excellent assembly distortion control Straightness in y-z (vertical) plane = +/- .030”

Straightness in x-z (horizontal) plane = +/- .011”

End to end roll = 9 mRad


Performance of Q5 L ChamberPerformance of Q5 L Chamber

HER Q5 L Installed Fall 2005

Beam induced heating of NEG dramatically reduced

HER Current (Mar 05-Aug 06)

Temperature of Q5 L NEG (Mar 05-Aug 06)


Q4 side, 10” Q4 side, 10” flangeflange

Q5 side 12” flangeQ5 side 12” flange

GlidCop GlidCop StubStub

Inconel Spring Inconel Spring FingerFinger

GlidCop RFGlidCop RF

Shield FingerShield Finger

Welded Welded BellowsBellows

Cooling – not shownCooling – not shown

Absorbing TileAbsorbing Tile

Mechanically decouples Q4 & Q5 vacuum chambers

Absorbing tiles above and below beam orbit

Q4/Q5 Bellows with AbsorberQ4/Q5 Bellows with Absorber


LER Q4 Right Temporary ChamberLER Q4 Right Temporary Chamber

LER Q4 R chamber replaced by a straight drift tube on22 February 2006

Concern that the chamber outgassing and/or sparking caused beam aborts (found to be not true).


LER Q4 & Q5 ChambersLER Q4 & Q5 Chambers

Two major issues addressed in redesign Beam induced NEG heating

(leading to NEG outgassing) Thermal motion of the Q2,4,5 raft/magnets

New design for LER Q4 & Q5 Improved RF screens Added “Flex Flange” at chamber inboard ends Improved mask cooling; also additional cooling

added

Old Screen New Screen

“Flex Flange” detail



Status Chamber fabrication and assembly complete

Q4 vacuum processing complete; Q5 chambers are on bake

Ready to begin installation of Q4 when project engineer returns on 26 October

“Flex Flange”prior to final assembly



Status Chamber fabrication and assembly complete.

Q4 vacuum processing complete; Q5 chambers are on bake.

Ready to begin installation of Q4 when project engineer returns on 26 October


DS-7 Octagonal-to-Round TransitionDS-7 Octagonal-to-Round Transition

Chamber absorbs a large amount of LER SR originating near the IP(1.2 kW @ 4.5 A, 3.1 GeV)

Previous DS-7 chamber not well cooled New chamber incorporates GlidCop body and

improved cooling Installed Nov 2005


LER 2062 ChamberLER 2062 Chamber

Vacuum leak developed on 10 Dec 2005 - sealed temporarily.

LER 2062 chamber replaced1 May 2006

Buttons in nearby chambers fell on 2 & 5 May, prompting effort to remove LER Collimator

Repaired chamber reinstalled on 16 May 2006

2062 chamber


LER 2143 CollimatorLER 2143 Collimator

LER 2143 Collimator removed 16 May 2006 Intended to control backgrounds in BaBar

HOM generator affecting downstream LER

Damage to the collimating surface being evaluated


Interaction Region HOM AbsorbersInteraction Region HOM Absorbers

High current running prompts a desire to manage HOM heating in the LER

Two HOM absorbing chambers to be added to the LER (3044 & 1153)

RF Shield 3.5 mm slots in 2.5 mm thick GlidCop

Uses Ceralloy 13740Y (Aln-SiC) tilesMatches existing LER Octagonal cross section

Install November 2006

Absorption (calculated by S. Novokhatski, S. Weathersby):Monopole – 0.0027%Dipole – 54%Other Dipole – 88%Quadrupole – 89%

Design selected for high absorption over a broad frequency rangeAll absorption curves relatively flat – no major spikes or troughs


Interaction Region HOM Absorber (1153)Interaction Region HOM Absorber (1153)

HOM Absorber

Octagonal to LER Arc Transition (New)

Elliptical to Octagon Transition

Octagonal Bellows

e+

Octagonal to Elliptical Mask (New)

Elliptical VAT Valve (reinstalled)

Improved masking at 1153 location


Additional DiagnosticsAdditional Diagnostics

Vacuum gauges added 9 additional hot filament gauges distributed through the

Interaction Region

These gauges are less sensitive to non-vacuum beam effects



Fast(er) data sampling SLAC standard history buffers store at 6 minute intervals

Data Archiver stores specified channels at 1 second intervals



(Really Fast) Abort Logger Multiple channels sampled

@1kHz for 10 seconds surrounding a beam abort

To date, only in place in IR-2; all other IRs added this downtime

Digital Video Recorder, Rotating Mirror, …


Goal – to create a HOM absorber in a defined modular space

HOM absorber will damp and absorb the power, preventing neighboring components from absorbing excessive HOM power

Design optimized with MAFIA simulations

Installed one unit on 1 May 2006

Three additional units deployed in Oct 2006

HOM Straight BellowsHOM Straight Bellows


Modes that leak past the RF shield finger still see the absorber

HOM Straight BellowsHOM Straight Bellows

Measurements confirm that the straight bellows-absorber in Region damped 40% of the available HOM power

Very good agreement with calculated performance of a 7cm length absorber


SummarySummary

The Interaction Region Vacuum System is receiving a major reworking in 2006

Principal efforts are centered around high current running

Management of synchrotron radiation and higher order mode heating has been addressed

Diagnostic capabilities have been developed and implemented to improve our abilities to understand future problems should they arise

We feel that the Interaction Region vacuum system will be ready to meet the demands of planned PEP-II operations

Documents

Interaction Region Vacuum Chamber Upgrades