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H0-H- PSB INJECTION VACUUM REQUIREMENTSC. Pasquino, P. Chiggiato, J. Hansen

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Outline• PSB H0-H- injection vacuum layout;• Graphite Vs SiC dump: resume;• Update on simulations with new cooling system;• Conclusions and actions.

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Linac 4 H-

PSB ring

RF shield

Stripping foil

Internal dumpSiC or Graphite

75 l/s SIP

75 l/s SIP

PSB H- Injection: vacuum layout

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Previous results resume

Graphite SiC10-10

10-9

10-8

Pre

ssur

e (m

bar)

Material

Dump at 175 C

N2 equivalent

Graphite SiC10-10

10-9

10-8

Pre

ssur

e (m

bar)

Material

Dump at 50C

N2 equivalent

P = 3*10-9 mbar P = 3*10-9 mbar

P = 6*10-9 mbar

ACTION GRAPHITE SiC

Vacuum firing Yes No

IN situ Bake –out (after each venting) Yes No

Active Cooling Yes Yes

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Influence of the new cooling systemMax. steady state temperature on chamber/flange: 88 °C for SiC and 83 °C for Graphite

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Influence of the new cooling system

Many parameters are involved in the definition of an acceptable temperature from the vacuum point of view: the materials, the heating rate, the pumpdown time.

Water vapor outgassing at 100 hours of pumpdown (a week of pumping);

Outgassing at 75 ◦C from the SiC; BSW4 surfaces at 80 ◦C and 50 ◦C;

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

BSW4 at 80C - transient

Par

tial p

ress

ure

(m

bar)

BSW 4

H2

CH4

CO CO

2

H2O

Ptot (N2 equivalent) = 2*10-7 mbar

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

BSW4 at 50C - transient

Ptot (N2 equivalent) = 2*10-8 mbar

Par

tial p

ress

ure

(m

bar)

BSW4

H2

CH4

CO CO

2

H2O

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Influence of the new cooling system

After a transient of few days of heating, the water vapor is released by the surfaces: H2 from the bulk is leading (H2 stainless steel outgassing).

The difference between the two temperature is very low.

10-15

10-14

10-13

10-12

10-11

10-10

10-9

Ptot (N2 equivalent) = 4.5*10-9 mbar

BSW4 at 80C - steady state

Par

tial p

ress

ure

(mba

r)

position

H2

CH4

CO CO

2

H2O

10-15

10-14

10-13

10-12

10-11

10-10

10-9

BSW4 at 50C - steady

Ptot (N2 equivalent) = 4*10-9 mbar

Par

tial p

ress

ure

(mba

r)

BSW4

H2

CH4

CO CO

2

H2O

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Actions and conclusions

The influence of the temperature has been studied in order to evaluate the vacuum impact: the choice of the final material of the vacuum chamber, the pumpdown time before beam impact, the heat rate are playing a fundamental role;With the boundary conditions considered above, only an active cooling leading to a surface temperature around 50 ◦C allows to stay within the vacuum requirements from the early stage of the heating;Finally some outgassing loads are still unknown (stripping foil mechanism) and need to be evaluated.

Period 1 (new injection)

Sector valves (old)

8 x Sector valves (new)8 x Ion pumps (new)8 x Gauges (new)

-Pumping group -Venting system(old)

-4 x Pumping group (new)-4 x Venting system(new)

Gauges and pumps (old)

Period 1 (new injection proposal)

Sector valves (old)

4 x Sector valves (was 8)8 x Ion pumps (new)4 Gauges (was 8)

-Pumping group (old)-Venting system(old)

-4 x Pumping group (new)-4 x Venting system(new)

Gauges and pumps (old)

Advantage:-More room for shielding.-Easy to vent and pumps without breaking foils. (big volume)-Leak detection, venting and pumping away from hot zone.

Sector approximately 9 meters (Fast Wire scanner not part of sector so only fragile object is the striping foil).