lcls-ii vacuum system specification

LCLS-II Vacuum System

M.J.Ferreira

Vacuum Science and Engineering Dep. Head

Mechanical Engineering and Technical Support Division

2

Outline

• Introduction,

• LCLS-II vacuum systems,

• Specifications for each system,

• Vacuum schematic fast valves,

• Lessons Learned,

• Hazards,

• Conclusions.

M. J. Ferreira OLAV IV, Hsinchu, Taiwan, April 01st – 4th, 2014

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Introduction

Conceptual Design for LCLS-II phase II Vacuum systems.

Main objectives:

• Clarify SLAC and partner laboratories interfaces of the vacuum

hardware,

• Review main specifications of sub systems and vacuum

instrumentation,

• Define interface: particle free and non particle free regions.


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LCLS-II Project


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LCLS-II project

IVC-19 Paris, September 9-13, 2013

Include LCLS-I

experience for the

injector: wave guide

windows, load

windows, vacuum

instrumentation for

fast response.

Old LINAC, a lot of

modifications along

the years:

necessary to

document and re-

simulate the

vacuum.

Noble gas for gas

attenuator soft X-ray:

Ar, Kr, Xe and Ne upto

50 Torr, windowless.

Use the exiting

PEP-II high

energy bypass

line.


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Basic Energy Science Advisory Committee

M. J. Ferreira LCLS-II Vacuum System CDR March 20th, 2014

LCLS-II project was reviewed and July/2013 presented to follow BESAC

recommendations at the Report on Future X-ray Light Sources.

• LCLS-II Phase II

CDR

September 2013

• LCLS-II phase II

Cost Review

January 22-24, 2014

• LCLS-II phase II

CD-1 DOE Review

February 4-6, 2014

Partner Laboratories:

ANL (undulator chambers)

Cornell Lab (gun)

FNAL (Cryo modules)

JLAB (Cryo modules)

LBNL (gun)

https://slacspace.slac.stanford.edu/sites/lcls/lcls-2/PublishingImages/collaboration_wd120.jpg

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LCLS-II phase II

LCLS-II CD-1 DOE Review, Feb 4-6, 2014

SXU

HXU

proposed FACET-II LCLS-I LCLS-II SC Linac

cross-over bypass line m-wall

A-line

B-line Sector-10 Sector-20 Sector-30 Sector-0

extension line L3 L2 L1

s (m)

Injector SRF Linac Transport Beamline

Dumps

Undulator hall

From BESAC report:

“It is considered essential that the new light source have the pulse

characteristics and high repetition rate necessary to carry out a

broad range of coherent “pump probe” experiments, in addition to a

sufficiently broad photon energy range (at least ~0.2 keV to ~5.0

keV).”

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LCLS-II phase II Vacuum systems

CM01 CM2,3 CM04 CM15 CM16 CM35

BC1

L = 92 m

R = 10 mm

BC2

L = 140 m

R = 10 mm Injector source Length = 2.1 m

Radius = 20 mm

LH L = 32 m

R = 10 mm

L0 L1 HL L2 L3

LTU

3.9GHz

L3 extension

L = 20 m

R = 24 mm

Differential

pumping

Diag. Line Diag. Line

Distribution

line

Pressure Requirements

Average Nitrogen equivalent Pressure:

Injector:

Injector source <1 x 10-10 Torr

SRF cryo modules beam line <1 x 10-10 Torr

Coupler <1 x 10-9 Torr

Thermal isolation <1 x 10-5 Torr

Laser Heater (inside low-particle region of the SRF) <1 x 10-9 Torr

BC3 extension <1 x 10-8 Torr

L3 to Bypass section max 1 x 10-8 Torr

Straight Ahead Beam max 1 x 10-7 Torr


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Vacuum Systems

The vacuum system of the LCLS-II phase 2 is consisted of 4 independent systems:

• The beam line system: is the vacuum related to the beam path along the machine,

including the injector, all cavities and instrumentations until the end-user stations. It

requires the lowest pressure at the injector and at the SRF section including, low particle

and leak rate requirements and restricted gas composition (LBNL, FNAL, JLab and

SLAC).

• The vacuum system for the couplers: what is design around each coupler as UHV

standard with ion pumps and TSP (FNAL and JLab).

• Thermal isolation system: is the cryostat vessel where all the thermal isolation is

contained including the cooling lines and the cavities (FNAL and JLab).

• The thermal isolation of the Cryogenic Distribution System (FNAL and JLab).


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Coupler Vacuum

The system is part of the cryo module assembly

(FNAL and JLab) and will include:

- The manifold to the couplers,

- The pumps (ion pumps and TSP),

- The pump down valve (angle valve),

SLAC will be responsible for the cables and

controllers. The pump down process, including

the turbo cart system will be SLAC responsibility.


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Injector Source

The system is a Very-High Frequency

gun (APEX) with the instrumentation

from LBNL, what will include all

vacuum hardware:

- Gun and load-lock system,

- All gauges, RGA and pumps,

- All diagnostic instrumentation.

SLAC will be responsible for the

cables and controllers. The pump

down process, including the turbo cart

system will be SLAC responsibility.

LBNL will work on the free particle condition and the vacuum performance of

the gun.

SLAC is working to help the 3D vacuum simulation for the VHF gun (APRX)

pump configuration and vacuum instrumentation.

Molflow +

Base pressure <10-11 Torr

Operation pressure <10-9 Torr


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Thermal Isolation vacuum system: cryo module

The thermal isolation of the cryo

modules will be provide by FNAL

and JLab, what will include the

following vacuum hardware:

- All vacuum gauges and isolation

valves,

- All the electro-pneumatic gate

valves (for each cryo module) for

pumping down the thermal

isolation,

- Burst disk for the thermal

isolation,

- Beam line pipe connecting the

cavities including the angle valve

and burst disk,

- Manual gate valves for the

cavities,

SLAC will be responsible for the cables and

controllers. The pump down process,

including the turbo cart system will be SLAC

responsibility.

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Thermal Isolation vacuum system: cryo module

SLAC will be responsible for:

- The roughing pump carts to pump down the thermal isolation,

- The turbo system attached directly to the thermal isolation to keep the

pressure in case of some unpredicted high outgassing or leaks.


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Thermal Isolation vacuum system: distribution line

SLAC will be responsible for the cables and controllers. The pump down

process, including the turbo cart system will be SLAC responsibility.

FNAL will be responsible to design and

deliver the distribution line including all

valves, instrumentation and assembling

process.


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Beam Line Vacuum

The Beam line vacuum will be a mix of LBNL, FNAL, JLab and SLAC parts what will include

the injector source, cryo module cavities, interconnections and warm sections.

• All the warm section will be responsibility of SLAC, from the vacuum flange of the cryo

module on.

Cleanliness requirements are pointed as procedures to follow for certification of free-particle

contamination of parts, assembling and installation process. A common ground about

procedures should be clearly state among the laboratories to assure equivalent results.

Specific point of contact are desired for easy communication.


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Beam Line Vacuum: differential pump X particle free region

At the actual stage the warm section design is envisioned the cleanliness near the cryo

modules as:

• Differential pumping and,

• Particle free region.

The warm section contains a series of instruments what some times can present technical

challenges to accommodate the cleanliness requirements.


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Particle free regions

Vacuum Guide lines:

• All materials and instrument shall be UHV

compatible,

• Able to be clean for particle free,

• No vacuum connection for external

systems (EX. Wave guide for T-cavity),

• Valves and vacuum gauges qualified for

particle free.

Pump down cart and venting:

• Specific turbo cart to run the pump down,

• Specific arrangement for venting process

• Specific configuration for leak detection,

Procedures among partner laboratories in

these subject can help SLAC to accomplish

the task in the cost and available time frame.


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L3 extension

The L3 extension will be using both solutions and a fast valve:

• Differential pumping,

• Particle free region.

The distance from the cryo modules to the L3 to Bypass (“DogLeg”) is around 300m.


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Fast valve system:

CM01 CM2,3 CM04 CM15 CM16 CM35

BC1

L = 92 m

R = 10 mm

BC2

L = 140 m

R = 10 mm GUN Length = 2.1 m

Radius = 20 mm

LH L = 32 m

R = 10 mm

L0 L1 HL L2 L3

LTU

3.9GHz

“BC3”

L = 20 m (2 km)

R = 24 mm

Fast signal: commercially

available cold-cathodes

for 3-4 ms from 10-11 –

10-7 Torr pressure rise.

Fast valve: commercially

available, radiation

resistant, UHV standard,

<10 ms (from signal to

leak tight).

Minimum distance 10 m. FS1

FS2 FS3 FS4 FS5 FS6 FS7 FS8

FV1 FV4 FV5 FV6 FV7 FV8 FV2 FV3

FV – fast valve

VS – fast signal

*

Isolation

vacuum

system

In case of a catastrophic failure, the fast valve system should be

able to close the valves (tight) before the gas wave reaches the

cryo module.

N2 gas speed (main gas in air) at room temperature 400 m/s, time

for 10 m distance 10 m/400 m/s = 25 ms.

*Only at the Gun injector a technical solution for a 2 m section

presents a question to be addressed more carefully.

The control system is able to answer much faster <1 ms.


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Lessons Learned

1. RF wave guides connected directly to the beam vacuum.

The vacuum requirements of a RF wave guide is substantially

different from the Beam line vacuum, and a physical barrier should be used

(EX: ceramic windows). The performance of the RF gun of the cavities can

be compromised as happened with LCLS-I RF gun.

LL: by design the Beam line will be physically separated from all other

vacuum systems.

2. Vacuum instrumentation (Cold-cathode and RGA) can change their

calibration and/or sensitivity over time. Any fixed set points or interlock can

be compromised, if regular maintenance and check up aren’t predicted.

Some cold-cathode gauges from Klystron was indicating measurements

under lowest limit, but the gauge sensor was actually damage.

LL: Schedule checks for cables, controllers and sensor heads.


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Hazards

Cryogenic:

Failure/rupture of cryogenic system from overpressure, mechanical damage, insufficient

or improper maintenance, improper procedures.

Probability after mitigation: remote

Mitigating Factor: design cryogenic per ASME, ANSI and SLAC Pressure Safety

program.

Applicable areas: Cavities, warm beam line, thermal isolation vessel (burst disk, relief

valves).

Accelerator Beam line:

Catastrophic loss of vacuum, cooling water, compressed air.

Probability after mitigation: remote

Mitigating Factor: engineered safety system to protect beam line from vacuum, cooling

water and/or compressed air faults.

Applicable areas: all vacuum systems interlocks, redundant systems and valves.

Accelerator system, mechanical system:

Compressors, pumps, cavities, HVAC, bake out and vacuum equipment failures.

Probability after mitigation: occasional.

Mitigating Factor: Separate areas from specific operation areas, isolation of

operation/experimental process, personnel safety devices (electrical, noise, etc).

Applicable areas: all vacuum systems and power supplies (HV).


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Conclusion

• A vacuum guide line need to be prepared among

laboratories to standardize vacuum equipment and

instrumentation,

•Action list need to be address to clarify interfaces and

point of contact for communications for the vacuum

systems,

•A series of documents need to prepared to cover all main

specifications, assembling and procedures among the

labs.

lcls-ii vacuum system specification

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