CESR-c Vacuum Performance

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1 CESR-c Vacuum Performance CESR-c Vacuum Performance Yulin Li, Yun He and Nari Mistry Laboratory for Elementary-Particle Physics Cornell University, Ithaca, New York, USA The 13 th ICFA Beam Dynamics Mini-Workshop Beam Induced Pressure Rise in Rings Brookhaven National Laboratory, Upton, NY December 9 – 12, 2003 CESR-c Vacuum

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CESR-c Vacuum. CESR-c Vacuum Performance. Yulin Li, Yun He and Nari Mistry Laboratory for Elementary-Particle Physics Cornell University, Ithaca, New York, USA. - PowerPoint PPT Presentation

Transcript of CESR-c Vacuum Performance

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CESR-c Vacuum PerformanceCESR-c Vacuum PerformanceYulin Li, Yun He and Nari Mistry

Laboratory for Elementary-Particle PhysicsCornell University, Ithaca, New York, USA

The 13th ICFA Beam Dynamics Mini-Workshop

Beam Induced Pressure Rise in RingsBrookhaven National Laboratory, Upton, NY

December 9 – 12, 2003

CESR-c Vacuum

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OutlineOutline

• CESR Layout• CESR-c Conversion

► Motivation and Objective ► Hardware Modifications ► Status and Performance

• CESR-c Vacuum System and Requirements

• Beam Conditioning and Wall-Pumping

CESR-c Vacuum

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CESR LayoutCESR Layout

CESR-c Vacuum

Principal Parameters:

768 m Circumference 1.5-6 GeV beam energy Y > 0.06 @(4S)

Ibeam > 350 mA

L > 1.2 x 1033 cm-2sec-1 @(4S)

45 bunches each e+, e-

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CESR-c Conversion – ObjectivesCESR-c Conversion – Objectives

CESR-c Vacuum

We propose to modify CESR to provide high luminosity colliding beams over the (beam) energy range from 1.5 to 5.6 GeV.

Energies (Ebeam) of interest and Luminosity goals:

J/: 1.55 GeV – 1.5 x 1032

Charm threshold (’’): 1.885 GeV – 3.0 x 1032

Above DD threshold: 2.1-2.5 GeV – 5.0 x 1032

states: 4.7-5.6 GeV – 10 x 1032

CESRc is designed to deliver 20-200x the world data sample in the 1.5-2.5 GeV (Ebeam) range during it’s proposed 3 year operation.CESR will be continuing to provide beams for SR BLs to CHESS

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CESR-c ModificationsCESR-c Modifications1. Extend energy range, reduce spot size at IP.

Replace PM IR quads with S.C. quads for full energy range, lower *, p.c. separation, and better solenoid compensation.

2. Reduce bunch length in proportion to spot sizeUpgrade RF system to shorten bunch length in order to take

advantage of smaller *.

3. Recover radiation damping lost at low energyInstall ~18 m of 2.1 T wigglers to control emittance and damping times.

CESR-c Vacuum

Items 1 and 2 have been previously planned and implemented as an upgrade to CESR performance.

The wigglers are the only major change specific to low energy operation.

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Status and PlanStatus and Plan

CESR-c Vacuum

► Completed CLEO-c Detector Upgrade this summer

► Six SC wigglers were installed this summer

► Six more to be installed next spring, that completes CERS-c conversion

Performance Achieved (Goal)

@1.88 GeV Beam Current (mA) – 135 (360)Lpeak (1032 cm-2s-1) – 0.4 (3.0)Int. Lum. /day – 1.6 pb-1

Accum. Lum. Exceeded BESII

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Vacuum Pumping in CESR-cVacuum Pumping in CESR-c

• SR induced desorption is much smaller in the most part of CESR

• Pumping in the Interaction Region (IP ±15 m ) are dominated by TiSP

• Distributed ion pumps (DIPs) in the arcs rely on dipole magnetic field and stop pumping @<700 Gauss (1.9 GeV)

• Fortunately, well-conditioned chamber walls function as effective getters (more later)

CESR-c Vacuum

1.0

0.8

0.6

0.4

0.2

0.0

Rela

tive

DIP P

um

pin

g S

peed

2000150010005000

Dipole Field (Gauss)

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Beam-Gas Loss LifetimeBeam-Gas Loss Lifetime

CESR-c Vacuum

Average pressure of ≤1 x 10-9 torr required

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““Wall Pumping” ExperimentWall Pumping” Experiment

CESR-c Vacuum

► Tests were made by turning off/on DIPs in a well instrumented sector of CESR while operating at 5.3 GeV.

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““Wall Pumping” ExperimentWall Pumping” Experiment

CESR-c Vacuum

► Measured pressure profiles are compared with one-dimensional calculations

► A ‘wall-pumping’ speed of ~110 l/s/m gives the best fits to the measured profiles

► DIPs were left off for several weeks

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SR Power ComparisonSR Power Comparison5.2 GeV 5.2 GeV vs.vs. 1.9 GeV 1.9 GeV

CESR-c Vacuum

1, ,Totalphoton Se Rb am SP F

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Beam ConditioningBeam Conditioning

CESR-c Vacuum

1, ,Totalphoton Se Rb am SP F

Two-Stage Beam Conditioning :

• Primary (direct) ‘beam-scrubbing” – Reducing on SR main-strip ( )SR

vheight

• “Activate” wall-pumping via scattered photons

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CESR-c Commissioning & CESR-c Commissioning & OperationOperation

• Starting commissioning in July 10, 2003• Alternating SR and CESR-c runs• Two CESR-c / CLEO-c ‘engineering runs’• Started 2.5-month CESR-c - CLEO-c ‘production’ run

CESR-c Vacuum

Init

al C

omm

issi

onin

g

SR Run

SR Run SR Run

CE

SR

-c M

S

CE

SR

-c M

SC

LEO

-c E

ngin

eeri

ngCESR-c MS

CLEO-c HEP Run

250

200

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100

50

0Am

p•H

r pe

r B

eam

340320300280260240220200

500

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300

200

100

0

Total A

mp•H

r

7/19 8/09 10/27 12/68/29 10/79/18 11/16

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Beam Conditioning – IR Beam Conditioning – IR

CESR-c Vacuum

0.1

1

10

100

1000

dP/d

I p (

ntor

r/Am

p)

0.1 1 10 100

Positron Beam Dose (Amp·hr)

East I R

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68

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68

1000

dP/d

I tot

al (

ntor

r/Am

p)

0.1 1 10 100 1000

Total Beam Dose (Amp·hr)

Hardbends

P=230•D-0.99

0.1 1 10 100 1000

Total Beam Dose (Amp·hr)

P=22.29•D-1

Sof tbends

0 – 8 m from 0 – 8 m from I.P.I.P.

8 – 15 m from I.P.8 – 15 m from I.P. 15 – 35 m from 15 – 35 m from I.P.I.P.

TiSP Pumped, Independent of Ebeam

Reduced Pumping @ L.E.

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Beam Conditioning – Arc Beam Conditioning – Arc

CESR-c Vacuum

1

2

4

6

810

2

4

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8100

2

4

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81000

dP/

dI to

tal (

ntor

r/A

mp)

0.1 1 10 100 1000

Total Beam Dose (Amp·hr)

“Main” ConditioningReduction of ph

Establishing the “wall-pumping”

35

30

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15

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0

dP/

dI to

tal (

ntor

r/A

mp)

500400300200100

Total Beam Dose (Amp·hr)

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Sustainable “Wall Pumping” Sustainable “Wall Pumping”

CESR-c Vacuum

6

81

2

4

6

810

dP/

dI

(nto

rr/A

mp)

0.1 1 10 100

Total Beam Dose (Amp·hr)

Well-conditioned sector In sectors where VCs have been fully conditioned, we do not see difference between the H.E. and L.E. operations

In sectors where VCs only been partially conditioned, NO deterioration over the current long L.E. run

20

15

10

5

0dP/

dI

(nto

rr/A

mp)

330325320315310305300295

J ulian Day, 2003

SC Wiggler Sector

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SummarySummary• With installation of six SC wigglers in CESR

and upgrade of CLEO-c detectors, CESR-c / CLEO-c program is performing well and on schedule

• The operation mode of alternating between the SR Run and L.E. HEP Run worked well (where H.E. SR Run acts as VCs conditioning)

• Vacuum ‘wall-pumping’ from conditioned VCs proved to be effective and lasting for the planned HEP program

CESR-c Vacuum