PEP-II Upgrade
Vacuum System

Machine Advisory Committee Meeting
December 13, 2004
Nadine Kurita

Outline Current & Energy Future Requirements
 Work Plan Status Near IR
 Far IR
 Diagnostics
 Additional upgrades Future upgrades Summary

PEP-II Vacuum p2

Upgrade Plan
Current & Energy Requirements
 LER – main ring
 Chambers design limit - 3.0 A on 3.5 GeV
 FY2005 Goal :FY2005 SR power is less than the design limit.

 FY2007 Goal:

3.6 A, 3.1 GeV
4.5A, 3.1 GeV

FY2007 SR power is less than the design limit.

 Verifying that all chambers met the original CDR design

parameters.

 HER – main ring
 Chambers design limit - 3.0 A on 9.0 GeV
 FY2005 Goal :FY2005 SR power is less than the design limit.

 FY2007 Goal:

1.8 A, 9.0 GeV
2.2 A, 9.0 GeV

FY2007 SR power is less than the design limit.

PEP-II Vacuum p3

Upgrade Plan
Current & Energy Requirements (cont.)
 Interaction Region (IR) LER Beam Power

Chambers design limit - 3.0 A on 3.1 GeV

FY2005 Goal : 3.9 A, 3.1 GeV
 FY2005 – 22% increase in SR power.



FY2007 Goal: 4.5A, 3.1 GeV
 FY2007 50% increase in SR power.

 HER Beam Power

Chambers design limit - 2.0 A on 9.0 GeV



FY2005 Goal : 1.8 A, 9.0 GeV
 FY2005 – SR power is less than the design limit.



FY2007 Goal: 2.2 A, 9.0 GeV
 FY2007 10% increase in SR power.

PEP-II Vacuum p4

Upgrade Plan
Other Requirements Increased HOM Heating, RF shielding Bunch Length

2004: 1.16 cm



2006: 0.9 cm

 Bunch Current

LER 45% increase

HER 30% increase New Lattice IR Lattice and BSC received 11/4/04

PEP-II Vacuum p5

PEP-II Work Plan
 Goal –create a work plan to reach the increased

luminosity schedule.
 Identified chambers for analysis to determine

upgrade needs.
 Created Vacuum System Shortlist


Looked at current limitations, operational failures and limits todetermine chambers that need to be evaluated and possibly
rebuilt.

Re-analyzed chambers.
 B1 LEB/HEB chamber Q2 Backward Chamber Q2 Forward Chamber Q1 Chambers
 Luminosity Chamber
 High Power Dump Chamber

PEP-II Vacuum p6

PEP-II Work Plan (cont.)
 Gathered drawings and design reviews for items on the

Shortlist.
Received additional documentation from LLNL.

 Strategize work for projected downtimes and short term goals.
 Opened Accelerator Improvement Projects
Completed preliminary conceptual designs



Detailed engineering estimatesOpened AIP projects
 Vertex Chamber B1/Vertex Bellows
 Q1/Q2 Bellows

 IR LER HOM absorbers
 IR Radial Ion Pump
 Q2 Backward Chamber

 HER & LER Q4/Q5 chambers

 HER & LER RF stations

 Q4/Q5 Bellows Module

 LER SLM

 IR HER HOM absorbers

 Frascatti Kicker

PEP-II Vacuum p7

IR Design Challenges
 Beam Stay-Clear and Magnet

Stay-Clear

Keep existing magnets
 Beta *s for HER & LER







Beta x* = 28 cm
Beta y* = 7 mm

Emittances for HER & LER

Emittance x = 60 nm-rad
Emittance y = 24 nm-rad

12 σ + 0 mm in X
 9 σ + 0 mm in Y Luminosity Cone : ~6.24σ
 Space Constraints

Outboard Q4R

Limits pumping, diagnostics,
cooling Limiting BSC through Q2 is 12 σ + 0 mm in X
 8.5 σ + 0 mm in Y
 New chambers will be within the
BSC defined by Q2.

Outboard Q5L
PEP-II Vacuum p8

IR Design Challenges
 HOM Power IR geometry inherently produces a trapped area
 Two larger ring chambers (BSC driven) into a small IP chamber Shorter bunches & higher current increases HOM power

trapped in the near IR chambers.
 Backgrounds
 Constrains chamber and mask geometries.

 SR power SR fans in this area have high linear heat loads.


B1R (Forward) is 660 W/mm. Three times higher than any linear
density in the PEP-II vacuum systemIntercepting B1 fans during mis-steers could cause permanent
damage to chambers – actively safe system required.
PEP-II Vacuum p9

Near Interaction Region Status

Q1 Chamber

B1 Radial Ion Pump



Spare vertex chamber exists.

Gold sputtering on hold forvertex bellows redesign.


B1 Chamber

IP

Vertex Chamber(not shown)

Plan on gold sputtering the SS
braze ends to reduce HOM and I2R
losses in this area.

Gold Sputter

Vertex Chamber DetailSt steel / Be braze joint
PEP-II Vacuum p10

Vertex Bellows Status Re-design Vertex Bellows
 TE power leaks past the RF shield and heats of the stainless steel welded

bellows and inconel fingers.

 Reduce power into the stainless steel welded bellows cavity.


Designed small cooled AlNiSiC absorbing tiles in the bellows cavity space.

 Design complete pending final design review

HOM and thermal analysis completed. (See J. Langton’s talk)

Cooling
Al Clam shell

RF Shield Fingers

Absorber

Inconel Spring Finger

PEP-II Vacuum p11

B1 LEB Chamber B1 LEB (R, Forward) masks

Groove for zero length y- mask
3rd Tip, 250 W/cm (3A)
375 W/cm (4.5 A) Power densities are about~660 W/cm (4.5A, 3.1GeV) on
first tip, from Q1 magnet.
Power density is high due toclose proximity of Q1 magnet& B1 chamber.
 New analysis combined with

fatigue test data and pull tests
indicates that masks are safefor 4.5 A.

Multiple Tips,
440 W/cm (3A)
660 W/cm (4.5A)

Holes for BPM

2nd Tip, 286 W/cm (3A)
429 W/cm (4.5A)
Primary Cooling Channels

 Delay making new B1 chamberManpower, cost, schedule Future spare B1 chamber.


Serrate other tips to reducestress levels.

4th Tip, 230 W/cm
345 W/cm (4.5A)
Secondary Cooling Channels,
Magnet Stabilization
PEP-II Vacuum p12

B1 HEB Vacuum Chamber B1 HEB –

Additional 10% power. Power from upstream Q4 magnet.
Engineering analysis reviewed and higher current operation should be acceptable.
Further review is in progress.

Elliptical blades are not a source of excessive HOM power.
 B1 HEB chamber will not be rebuilt.
Inside contour turned from OFE
copper bar, then halves e-beamwelded together

Holes for BPM
feedthroughs

Au-tip reduces scatteredphotons into SVT
Tip radius is 100 µm

Outside shape fits into
stepped-aperture B1 Magnet

Elliptical mask scrapes Q4 SR halo
PEP-II Vacuum p13

Q1 Chamber Q1 Chamber will not be rebuilt.
 Background blade masks.
“Blade” masks are thin and abrupt, does nothave a 1:10 taper.

Only increases the broadband, but doesn’t
effect the narrowband impedance.


Therefore, making a smooth background mask
would not reduce the HOM’s stored in the IR
chambers.

 Power on mask tips.


Q1B (Forward)

Z=-1600mm (vertical) – no power

Z=-1100mm(elliptical)
 150W (2A, 9 GeV), HEB Q4 mask

Q1B (Backward)

Z= 950mm (elliptical)
 680 W (3A, 3.1 GeV), 1020 W (4.5A), LER
BV1 fan q” = 694 (3A), 1041 W/cm2 (4.5A)



Z = 1200 mm (vertical) – no power

Scaling thermal results indicate masks arewithin stress limits at 4.5A.

PEP-II Vacuum p14

B1 Radial Ion Pump
 New Design Complete pending

final design review.
 Addresses current pump issues


Argon Instability

Noble diode pump, rebuild withtantalum plates

Pump failures

Two circuits,Higher rated feedthru designImproved mechanicalfabrication designVerified pump screen issufficient with new bunch
parameters

Reduce pump physicaldimensions to add additional
BPM set.

No additional shielding New pump ready for installation2005 Summer Downtime.
PEP-II Vacuum p15

B1 Radial Ion Pump
Prodec Anode cell structure
Ceramic Standoff

Tantalum/Titanium
Cathode Plates
Additional
BPM setReduced to 4 cellarrays from 6.
Shorten pump to
add BPM set.



Modified to Ta
from Ti to increase
noble gas pumping
and eliminate theargon instability.

Baffles∅2mm holes

PEP-II Vacuum p16

Beam Position Monitor (BPM) Upgrade improvements
 Added BPM set at each radial ion pump.
 The new set is separated in z by ~f * 7.9 cm fromthe BPM’s in the B1 chamber, where f = 2.

 7.9 cm corresponds to a quarter wavelength of

952 MHz, the BPM procesing frequency.
In the electronics they can then synthesize
independent linear combinations of the signals
which correspond to the two beams moving in
opposite directions.

~2*7.9PEP-II Vacuum p17

Q1/Q2 HOM Bellows
 FY2003 added 4 layers of tiles per module.
 Absorbing ~10 KW presently Predict ~ 50 KW in 2007
 Numerous iterations on HOM absorbers

have been analyzed by S. Weathersby and
A. Novokhatski (38 runs).


Goal: Create a HOM absorber that doesn’t
generate ~50% of its absorption power.


Reduce monopole without significantly reducing
dipole and quadrupole modes

Most effective design requires at minimum 4” slots
as in the Straight HOM Bellows.



The optimized design for various modes must be
chosen by February 2005.


A few more design/analytical iterations will be
performed



Reduce power absorption, but still reduce HOM
power at the vertex ends, vertex bellows and radial
ion pump.
Vertex bellows will have HOM tiles

Gold plating will be extended on the vertex ends.

PEP-II Vacuum p18

Q1/Q2 Blws - HOM Analysis
 4” long tile sets
 Suppresses the monopole mode

without reducing the dipole andquadrupole mode
 Sasha calculated the set back of thetiles Focusing on 2” long tile sets
 Reasonable length for the 5”

bellows module

PEP-II Vacuum p19

Q1/Q2 Blws - Design Status
 New concept

developed based on best

information
available.
 Maximum

Tile/slot length ~2.4”

 Absorbing tiles

is open to the
convolutions
 No additional tile

set needed inbellows cavity.
 HER Arc Style

Bellows
 Spring
Possibly reduce

further the travel andoffset requirements toincrease length.

 Stub RF shield

PEP-II Vacuum p20

Far IR

HER- Downstream, “Forward”, “Right”
9.4M

8.4M

5.7M

19.5M

2.3M

3.6M

High-Power Frangible Link
Dump

Q5R

Q4R

Q2R

0.0 M

IP

HER- Upstream, “Backward”, “Left”
0.0 M
3.6M

2.3M

7.7M

5.7M

IP

Q2L

Q4L

Q5L

8.5M

10.1M

11.4M

Frangible “Luminosity 10M
Link
Chamber”
PEP-II Collimator
Vacuum p21

Q2 Chamber (cont.)
 Q2L (Backward)


8KW from LEB B1 and Q1

Designed for three conditions
 Solonoid on Solonoid off Solonoid not thereHeat Loads
 Power density was highest in

the ‘NO” solonoid condition
because it placed two beams
in the same spot on the mask.

Q2L Wedge Mask

 Re-analysis of chamber will

be done with new geometry,lattice and current.
 Analysis scheduled forJanuary.
Currently no plan to rebuild
this chamber.
PEP-II Vacuum p22

Q2 Chamber
 Q2R (Forward)Replaced Q2R with a Q2L chamber in 2002.
 Increase BSC acceptance and reduce HOM.
 Failed due to material flaw in the GlidCop.



Original Q2R chamber replaced in 2003.
 Clips BSC
 No evidence that it creates increase HOMs.

New Q2R is in fabrication.
 Some parts received.

A. Sheng Complete by April 2005.



Thermal analysis completed.
 Simplified 3D extrusion and no finswere included in the model.
 Peak ΔT= 139 C (tip of the maskfrom QD4.8).

 Water wall ΔT = 58 C.

QD4.4
QD4.5
QD4.6
QD4.7
QD4.8

LengthQ
Power(inch) (w/cm) (w)
2.2008 104.9 586.12
2.248 90.73 518.06
2.0472 88.64 460.92
1.9094 83.95 407.17
0.6654 212.3 358.82

Q4 Total

2331.1beam
ht (in)0.02980.03
0.03010.03040.0307Peak
power
density(W/in^2)
8934.792
7687.311
7467.797
7022.742
17590.1

PEP-II Vacuum p23

Outboard of the near IR Q5 & Q4 HEB Chambers
 General problems
Mechanical & HOM failures in the NEG screensBeam Stay Clear (BSC) & Lumi cone.



Thermal motion issues?

Magnet instabilities



Q4 & Q5 are rigid chambers that have minimal to no clearance to their respective magnets.



Load on Q2 chamber, IR support
raft, magnets

Global alignment error between
the “Bong” Collimator and Q5.

 Q5R (Forward End)

Flange heating

Neg screen destorted

 Q5L (Backward End)

Masks failed and replaced

Neg screen detached Q4R (Forward End)
 Q4L (Backward End)

Masks failed and replaced

PEP-II Vacuum p24

HER Q4 & Q5 Chambers
 Status
 Received detailed

documentation from LLNL 6/04
 Received vendor quotation for

Al clamshells.

 Modeled existing magnets andchambers.
 Thermal and structural analysis completed.
 Final Design Review 2/05
 Ready for installation 8/05

PEP-II Vacuum p25

HER Q4/Q5 Chambers
 Goals achieved LER:

4.5A, HER 2.2 A

 Designed between the defined BSC/luminosty cone andexisting magnets
 Maintain a 2mm gap to poles and a 3mm gap to coils.
 Reduce thermal gradients

Aluminum clamshell design

 Added a bellows between Q4, Q5
 Improve kinematics andstabilize BPM supports
 Decrease the TE leakage

to the pumps

Screen hole diameter reduced
to 3 mm and depth increased
to 6mm.
PEP-II Vacuum p26

Q4/Q5 Bellows Module
 HER arc bellows

concept +absorbing tile inbellows cavity.

Q4 side, 10”10”flangeInconelSpringFinger Design Review

12/05
Absorbing
Tile

GlidCop
Stub
WeldedBellows
Cooling – notshown Final Design

Review 2/05
 Complete 10/05

GlidCop RF
ShieldFinger
Q5 side 12”12”flangePEP-II Vacuum p27

Q4/Q5 Blws Detail Design HER Arc Bellows concept withabsorber Ensure failure does not result in

the RF shield falling into beamtube
 Shield fingers slide on outside ofchamber stub
 Keep high stress areas awayfrom high heat areas Keep steps to a minimum,

reduce impedance Plating to minimize wear,
decrease cold welding, solid
lubrication
PEP-II Vacuum p28

LER Q4/Q5 Low pressure chambers
 Two major issues led to redesign
 NEG heating problem
 Thermal motion of the backward raft/magnets.

 Status
 NEGs removed this summer and absorbers added to pump passages.
 Added TSP/Ion pump manifold and absorber to LER Q4R Chamber.

LER Q4R Absorber
LER TSP/Ion pump manifold

PEP-II Vacuum p29

LER Q4/Q5 Low pressure chambers
 New design for Q4 and Q5 chambers underway (see J. Langton’s talk).
 Improve RF screens Add cooled HOM loads (TBD)
Old Screen

New Screen

PEP-II Vacuum p30

High Power Beam Dump
 Current design limit 1.5 A, 9GeV
 47% increase of SR at 2.2A
 10 – 21 m from IP on forward side.

 Chamber re-analyzed for 2.2 A, 9GeV
 High power beam dump (HPBD) is subjected to 127 kw

PEP-II Vacuum p31

High Power Dump Chamber ΔTmax = 72 C at section 3.
 σmax = 13 KSI (combined

thermal and mechanicalstress).


In half hard copper and notin the weld joint.

 Temperature analysis fits wellwith thermocouples data.
 HPBD is passively safe at

HER beam current 2.2 A.
A. Sheng

PEP-II Vacuum p32

Luminosity Chamber
 Chamber reanalyzed
 2,560 W of LER @ 4.5 A,
B2 and B3
HER 323 W of HER @ 2.2 A,
 10% reflected power(288.3 W)

B1B, B1C, B1D, B1E,
B1F LER 1kW/m HOM (1,625 W)

 ΔTmax = 65 C at mask tip.
 σmax = 16 KSI (combined

thermal and mechanical stress).
 Luminosity chamber is safe

at LER 4.5 A andHER 2.2 A beam current.

PEP-II Vacuum p33

HER Moveable Collimator Chamber screen is not passively safe for > 1A on

3.5 GeV during a vertical mis-steer
 Run with the known risk and have a spool ready if

it fails from a high current mis-steer.
 Build new chamber for 2006
 Fixed collimator HER absorber added to chamber

 Status
 AIP started
 New chamber designs

N. Reeckunderway HOM calculations performed

and designs is being optimized
to absorb HOMs.

PEP-II Vacuum p34

Diagnostics Upgrades Diagnostics
 Transverse Feedback

Chambers


Thermal/power issues
 Kicker feedthrus/connectors
 Aluminum electrode

New Molybdenum electrodeand flexure design complete
and fabricated.



Spare chamber retrofited withnew electrodes and flexures.

Installed this summer.

PEP-II Vacuum p35

Diagnostics Upgrades Longitudinal Feedback

Chambers

Fracati style kicker
completed and installed thissummer SLM (LER)

Modified LER pumping
chamber and special photonstop installed this summer.
 Front-end components andnew diagnostics installed
this summer.
 Alan Fisher will discuss thisproject in detail on Tuesday.
PEP-II Vacuum p36

Additional Upgrades Others
 LER Abort Window

Re-analyzed and verified that it will notsurvive 4.5A.

Possible to build a Ti window, but it would
be difficult to retrofit existing chamber.



Titanium spoiler will be placed upstream of
window.
 More cost effective
 HOM analysis in progress Elliptical & Round ValvesElliptical valves have failed in several
location.



Delay rebuild of valves

Test a HOM absorbing bellows near valves.

LER Abort Spoiler
M. Dormiani
PEP-II Vacuum p37

HOM Absorbing Bellows
 New bellows designs that also function as

beamline HOM absorbers.
 LER arc bellows
 Straight bellows
 Q2 bellows

 New bellows designs that have absorbers that

protect themselves from modes that leak behind
their RF shields.
 Vertex bellows
 Q4/Q5 bellows

PEP-II Vacuum p38

Straight HOM Blws -Design Details
Absorbing Tile
Inconel Spring
FingerGlidCopStub

2.75”
2.75” long by .24”
.24” wide
HOM Trapping Slots
Modes in the chamberpropagate through the slots &are absorbed by the AlNiSiC.

GlidCop RF
Shield Finger

WeldedBellows

Bellows Cavity
Modes that leak past the RFshield finger and are trapped inthis area still see the absorber
PEP-II Vacuum p39

Straight Section HOM Bellows
 Prototype of the HOM absorbing bellows
 Simple round geometry
 Locate near isolation valves to tests its impact on HOMs inneighboring components.
 Conceptual design complete HOM calculations are being done to optimize tile

size and slot dimensions.
 Initial HOM analysis shows that the concept

works.
 Reduces monopole absorption while optimizing dipole andquadrupole field absorption.

PEP-II Vacuum p40

Upgrades
 HER IR-2 transitionConceptual design complete.



Thermal & structural analysis underreview.



Final design review Jan ’05.



Ready for installation Aug ‘’05.

 Future Upgrades
 HER & LER Frangible Links-Lumi

Meets current requirementsPossible rebuild in the future for
improved maintenance.

PEP-II Vacuum p41

Future Upgrades (cont.)
 LER photon stopsDesign reports indicate that the photon stops were designed for 3A and3.5GeV, therefore it can handle 4.5A on 3.1GeV.



We will re-analyze the photon stops prior to 4.5A operations.

Transient analysis needed for water failure scenario
 Design in MPS to prevent failure during loss of water.

 Flow switches are costly and could cause excessive spurious trips.
 RTD or klixon – transient analysis needed LER Wiggler Vacuum (IR6)

BPM – TE mode problems,

Need to re-examine wiggler power and bend magnet power – water
channel problems.

 IR 10 Wiggler (NEW)

Required to reach higher luminosity

PEP-II Vacuum p42

Vacuum Calculations
 Lou Bertolini’s and Mike

Sullivans vacuum
calculations were updated
this year.

 Rebuilt the geometry/

conductance/ pumping
from drawings of theexisting IR.

 New vacuum calculations

should be complete earlynext year.

 Local areas are being

reanalyzed in ANSYS.

 Improved PSD rates areplaned to be used.

 2 orders of magnitude lower.
PEP-II Vacuum p43

Summary Progress Chambers needed for the upgrade have been identified and prioritized

Vertex Bellows
 Radial Ion Pumps
 Q1/Q2 Bellows
 Q2 Forward Chamber
 HER & LER Q4/Q5
 Q4/Q5 Bellows
 BPMs LER Abort window HER IR transition
 LER bellows prototype
 HER IR Collimator Work load has been reduced

Re-analyzed chambers and determined that they should survive the new beam
parameters.
B1 LEB & HEB
 Q1 LEB & HEB
 High Power Dump Chamber Luminosity Chamber Q2 Backward Chamber (TBD)

PEP-II Vacuum p44

Summary (cont.) Chambers required for the summer ’05 downtime

have progressed and fabrication will start at the
beginning of ’05 and be ready for installation
during the fall downtime.
 New hardware to be installed for the ’06 downtime

have also been identified and projects are also
progressing.

PEP-II Vacuum p45