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Vacuum Pressures at IR. Y.Suetsugu KEKB Vac. Group. Contents. Outline of Vacuum System at IR Behavior of Pressures Remedies for Heating of Vacuum Components. Vacuum System at IR.

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Vacuum Pressures at IR

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Vacuum pressures at ir

Vacuum Pressures at IR

Y.Suetsugu

KEKB Vac. Group

Contents

  • Outline of Vacuum System at IR

  • Behavior of Pressures

  • Remedies for Heating of Vacuum Components


Vacuum system at ir

Vacuum System at IR

  • Here IR (Interaction region) means the straight section in ±~100 m from IP (Interaction Point), especially upstream side of each ring.

  • Material of beam duct: OFC (Oxygen Free Copper) for most part (both rings). Aluminum alloy for complicated chamber just near to IP.

[Aluminum Alloy]

[OFC]


Vacuum system at ir1

Vacuum System at IR

  • Vacuum pump: Main pump = NEG (st707) : almost every 1 m (0.2 m3/s), Auxiliary pump = Ion pumps : almost every 10 m (0.2 m3/s). In average, about 0.7 m3/s/m just after an activation of NEG.

NEG cartridge

(arc section)

NEG module

(just near to IP)


Vacuum system at ir2

Vacuum System at IR

  • Vacuum gauge = CCG (Cold Cathode Gauge) just above ion pumps (every ~10 m). A small dipole magnet (permanent magnet) is attached at the neck of gauge port to eliminate photoelectron effect.

Without Manget

CCG

~100 G


Vacuum system at ir3

Vacuum System at IR

  • Location of Gauges and Pumps near to IP

HER

LER

D01_H02

D02_H23

IP

D01_H02A

D01_H01A

D02_H23A

(D02_H24)

[Inside of BELLE Solenoid]

Integrated NEG

Integrated NEG

0

10 m

5 m


Vacuum system at ir4

Vacuum System at IR

  • HER Upstream Side (straight section, ~100 m)

  • Straight : No bending magnet

  • Gauges: every ~10 m

D01_H01A

D01_H03

D01_H02A

D01_H04

D01_H05

IP

GV

GV

D01_H06

D01_H7

D01_H8

GV

BS

D01_H10

D01_H09

D01_H11

HER


Vacuum system at ir5

Vacuum System at IR

  • LER Upstream Side (straight section, ~100 m)

  • Local correction region: 13 bending magnets

  • Gauges: every ~10 m

LER

D02_L16

D02_L17

GV

BS

GV

D02_L19

D02_L20

D02_L18

IP

GV

D02_L21

D02_L22

D02_H23A

D02_L23

D02_L24


Behavior of pressure

Behavior of Pressure

  • HER_1

Three days

including several

beam Injections.

D01_H04

D01_H03

D01_H02A

D01_H01A

IP

D01_H06

D01_H7

D01_H8

2x10-7 Pa

Heat Source

= Gate Valve

P

Big BG Source

0

0

1.4 A

Ib


Behavior of pressure1

Behavior of Pressure

  • HER_2

Three days

including several

beam injections.

Gate Valve

D01_H7

D01_H8

Gate Valve

D01_H06

D01_H09

Heat Source

= HOM Absorber,

Taper

D01_H10

D01_H11

Heat Source

= Stopper (~ Gate Valve)


Behavior of pressure2

Behavior of Pressure

Three days

including several

beam aborts.

  • LER_1

? (NEG?)

D02_L20

D02_L18

D02_L19

IP

D02_L21

D02_H23A

D02_L23

Heat Source

= Gate Valve

D02_L22

D02_L24

3x10-7 Pa

P

Heating +NEG?

Multipactoring?

0

0

2.0 A

Ib


Behavior of pressure3

Behavior of Pressure

Three days

including several

beam aborts.

  • LER_2

Heat Source

= Taper

Heat Source

= Stopper

D02_L16

D02_L17

D02_L15

Gate Valve

Gate Valve

D02_L19

D02_L20

D02_L18

? (NEG?)


Present status

Present Status

  • The pressures near to IP is <1x10-7 Pa for HER and ~2x10-7 Pa for LER at the maximum operation current.

  • The pressures at upstream side of IP (IR) is almost less than 1x10-7 Pa,but affected by the heating of components, such as gate valves, stoppers, HOM absorbers and NEG(?).

  • The same harmful effect by heating can be seen widely in arc sections too. A major problem for further improvement of pressure.


Remedies to heating

Remedies to heating

  • Main reason of the heating is HOM.

  • Heating of Gate Valves, Stoppers and Bellows

    • Finger-type RF shield is not enough for high current

    • TE mode can easily coupled to modes outside

  • Tentative measure = Cooling from outside

[Gate Valve]

symptomatic therapy

[Bellows]


Remedies to heating1

Remedies to heating

  • Future (more essential) measure

    • Proposal of a New RF-shield structure

    • Comb-type RF-shield

  • 6 circular-type and 1 race-track-type has been installed in LER, and showed good results.

  • Application to gate valves are now planed and a test model will be installed in the ring this winter.


Remedies to heating2

Remedies to heating

  • Heating of NEG

    • Gas desorption from heated NEG had been observed near collimators.

  • HOM (TE-mode) intruded through a grid into pump port.

  • Tentative measure = use a special gasket

f = 6 mm

t = 2 mm

Cu

Lead to heating of other components

  • HOM absorber were installed finally.


Remedies to heating3

Remedies to heating

  • Heating by other HOM sources, such as collimators or tapers.

  • Install HOM absorber chamber

    • Example installed near collimators

    • HOM absorber = SiC

SiC

Slot

Wing

SiC

Beam Chamber

Require Space ! How about IR?


Summary

Summary

  • The pressures at upstream side of IP is almost less than 1x10-7 Pa, but also affected by the heating of components, such as gate valves, stoppers, tapers, NEG and HOM absorbers.

  • The problem had been solved accordingly so far. But, essential (drastic) remedies, such as employing new RF-shield or installing HOM absorbers, will be required for future high current operation.

  • Improvement of pumping speeds and cooling capacity are of course important.


References

References


Present status1

Present Status

  • Typical Run(11/09/2004)

Beam Current

1.2A x 1.6 A

Lifetime

230, 180 min

Ave. Pressure

10-7 Pa

Luminosity

~1.1x1034cm-2/s

Beam currents are usually limited by any problems in vacuum components


Present status2

Present Status

(If S = 0.3 m3/s/m)

  • Vacuum Aging (arc section, -2004/10/31)

    • DP/DI : 1x10-7 Pa/A

    • Photo-desorption coefficient,h : ~ 3x10-7 mole./photon

    • Effect of photoelectrons were eliminated by magnets.

    • HER seems to be effected by heating of components.

[LER]

[HER]

DP/DI

DP/DI

Max. I

Max. I

[Pa/mA]

[Pa/mA]

PM

PM

[mA]

[mA]

(Corrected)

[PM]:Set permanent magnets to every gauge port


Present status3

Present Status

Just near to GV!

  • Vacuum pressures in HER (~300 gauges)

(ARES)

(ARES)

(SCC)

(SCC)


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