Updated Status of the PAL-XFEL Vacuum System · PDF fileUpdated Status of the PAL-XFEL Vacuum System . April. 2, ... Special extrusion die . ... LVDT corrector. corrector

Updated Status of the PAL-XFEL Vacuum System

April. 2, 2014

Donghyun Na PAL VACUUM GROUP

POHANG ACCELERATOR LABORATORY

포항가속기연구소 Pohang Accelerator Laboratory

The design and fabrication procedures are basically based on the previous work done by the vacuum group

of LCLS, European XFEL, PSI and FERMI@ELETTRA.

We thank to them for the helpful discussions and the

reference materials!

Acknowledgement


Contents

I. Introduction of PAL-XFEL

II. Linac Vacuum system

III. Undulator Vacuum system

IV. Summary


Schedules for Fabrication and Installation

2012 2013 2014 2015 2016

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

Installation start

Extrusion test (U-chamber)

Completion of installation

RF conditioning start Injector commissioning

Commissioning start

Abrasive flow polishing test

1st prototype (BC, Collimator) 3rd prototype (U-chamber: Ver. 3)

1st prototype (U-chamber)

2nd prototype (U-chamber: Ver. 2)

Purchase order (Gate valve, CCG…)

2011

Concentrated on Al surface study

XFEL project start

ITF installation

Purchase order (Small vacuum components)


July 20, 2013 August 2, 2013

March. 18, 2014

Building Construction

Dec. 2013


Injector Linac

Undulator


Vacuum system Requirement

- Pressure @ RF gun ~ 1 x 10-10 mbar (cathode lifetime, dark current)

- Pressure @ Accelerating column < 5 x 10-7 mbar (RF break down)

- Symmetric beam pipe and RF shielded components are needed

RF photocathode gun (Cu cathode) - VTO technology (STS chamber, 450oC, 24 h, 1E-9 mbar O2) - P~3E-11 mbar without RF power - Less than 5E-10 mbar with RF power

Injector Vacuum

- Outgassing rate: 2x10-14 mbar l/s cm2


- Pressure @ Klystron window < 5 x 10-8 mbar (RF break down)

- Pressure @ Accelerating column < 5 x 10-7 mbar

- RF shielding for joint and bellows are not needed (?)

Linac Vacuum

Vacuum system Requirement

- Surface roughness < 200 nm (100 nm)

- Surface oxide layer < 5 nm (10 nm)

- Pressure < 1 x 10-5 mbar (beam-gas interaction)

- RF shielding for joint and bellows are needed

Undulator Vacuum


Layout of Linac Vacuum

SIP(60 l/s)

CCG

SIP(60 l/s)

CCG

L1 L2, L3, L4


Pressure profile of the accelerating colummn

(In case for some SIP failure)


Modeling of Bunch compressor2

Bunch compressor Vacuum system


1st Prototype of Bunch compressor2 Dimension of Bunch compressor2


Requirements of Bunch compressor

Bunch compressor Vacuum system

Al6063 T5 (Extrusion) Bimetal flange - Friction welding


• Bending Magnet Vacuum chamber (rectangular) 1) Inner dimension: 100 x 25 mm, thickness 2 mm 2) roughness: < 250 nm 3) material: Al6063 4) relative permeability(μr): < 1.03

• Drift chamber (circular) 1) O.D 42 mm, I.D 38 mm for Quadrupole chamber 2) O.D 100 mm, I.D 92 mm for Drift chamber 3) relative permeability(μr): < 1.03 for Q-chamber

• Diagnostic section 1) Two sputter ion pump near diagnostic instrument to reduce pressure rise induced by collimator, slotted foil and screen 2) One cold cathode gauge to measure pressure 3) E-BPM, Collimator, Slotted foil, Screen will be placed

1st Prototype of Bunch compressor2

Vacuum gauge

Slotted foil

Energy BPM

Screen

Energy collimator


Collimator (Energy and Geometry)

Energy Collimator Geometry Collimator


Requirements of Collimator

Collimator (Energy and Geometry)


1st Prototype of Collimator Vacuum system Modeling of Collimator


288 mm Individual jaw movement

OFHC Cu

1st Prototype of Collimator Vacuum system


Layout of Undulator Vacuum


Layout of Undulator Vacuum

s SIP

1 2 3 4 5 6 18

s SIP s SIP s SIP s SIP s SIP s SIP s SIP s SIP s SIP s SIP

17 16 7

s SIP

Seeding section

(No space for gate valve between U-chambers)

(20 L/s)

HX Undulator

5 m 1 m CCG CCG

8

s SIP


(Ver. 3)

LCLS PAL Ver. 2 PAL Ver. 3

Undulator Length [m] Undulator Gap [mm] Saturation length [m]

3.4 6.8

5.0 7.2

115.7

5.0 8.3

128.8

Quantity (required/fab.) Material Aperture (VxH) [mm] Thickness [mm] Flatness Clearance(pole to ch.) [mm]

33/40 A6063-T5

5 x 11

0.5±0.05 < 50 0.4

33/40 A6063-T5/T6

5.2 x 11 (racetrack)

0.5+0.05,-0.1 < 100 0.5

33/40 A6063-T5/T6

6.7 x 13.4 (elliptical) 0.4±0.05 < 100 0.4

Change of Undulator and Vacuum Chamber


Change of U-Chamber Cross section


Die / Tip Design & Build

0.5 mm ± 10 um Precision Machining Abrasive Flow Polishing

Surface Analysis

6m extrusion chamber

U-Chamber Fabrication Procedure

Extrusion in the controlled gas environment

Controlled gas (Ar + O2)

Special extrusion die

Special extrusion procedure

To prevent exposure to ambient air during extrusion process

Vacuum chamber

Gas hole

Extrusion tip


①

②

③

④

⑤

⑥

⑦

Chemical polishing procedure


Chemical polishing system diagram


0.5 mm ± 10 um

Chamber thickness

0.51

0.52

0.53

0.54

0.55

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

(mm

)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

(mm

)

0.5 mm ± 100 um

Precision machining results

(Ver. 1)

(Updated)


Precision machining results

-0.05

-0.03

-0.01

0.01

0.03

0.05

1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031(mm

)

Less than 30 um

Chamber flatness


Roughness Result Roughness measurement after abrasive flow machining

∫=l

xa dxfl

R0

)(1

270nm

200 nm

100 nm

300nm

130 nm

40 nm

640x640 (um)

270 nm 300 nm

beam direction perpendicular direction

1.8 um

1.1 um

0.6 um

extrusion only

extrusion & AFM

SiC#600 40hrs

extrusion & AFM

Al2O3#320 40hrs

420 nm

151 nm

83 nm


Oxide thickness - TEM images May, 2013


Oxide thickness - TEM images March, 2014

Abrasive flow polishing

Chemical polishing

Test is ongoing


Undulator Inter-section (ver 3)

LVDT corrector

phase shifter quadrupole cavity BPM

pumping spool

corrector limit sensor mover beam loss monitor Limit sensor

Beam direction

Undulator and Intersection Vacuum system

Length 1 m



Cross section of Undulator Intersection

RF shielded Al tube in Pumping spool

Inter-section Vacuum chamber

Undulator and Intersection Vacuum system



QM chamber (Al, I.D 9 mm)

bellows (SST 316L)

Al tube(I.D 9 mm) (for RF shield)

friction welding

Aluminum welding RF contact

RF contact

Pumping slit (Al, 20 x 1 mm, 10 ea)

Al tube(I.D 9 mm) (for RF shield)

bellows (SST 316L)

undulator chamber (Al, 6.7 x 13.4 mm)

Undulator intersection (cross section)

Beam direction



undulator chamber (Al, 6.7 x 13.4 mm)

Phase shift chamber (Al, I.D 9 mm)

bellows (SST 316L)

Al tube (I.D 9 mm) (for RF shield)

friction welding Aluminum welding Al tube(I.D 9 mm)

(for RF shield)

PNW-15 flange (SST 316L)

BLM (O.D 19 mm)

Undulator intersection (cross section)

Beam direction


Ф11 Ф9 Ф11

Ф9

Ver 2

Ver 3

5.2 x 11 mm (race track)

Phase shifter chamber BPM Quadurpole chamber

Quadurpole chamber BPM Phase shifter chamber Pumping spool

Pumping spool

Minimized Cross section change


Reduced welding joint steps


3rd Proto-type Undulator intersection

Friction welding (SST316L / Al6063)


Pumping down test of U-chamber


Pumping down curve

20 h to reach 1E-6 torr


Summary

Injector vacuum • Combination of SIP and NEG is used for the gun vacuum (low 10-10 mbar) • ITF vacuum installation finished & commissioning is on going • ITF gun vacuum will be optimized for the PAL-XFEL gun

Linac vacuum • Much experience of S-band linac vacuum system with PLS-II linac

Bunch compressor, collimator • Design of bunch compressor and collimator finished recently • Purchase order of the 1st prototype BC in 2013.11 • 1st prototype collimator is fabricated (2014.03)

Undulator vacuum • 3rd prototype of U-chamber is now being fabricated • Satisfies RF requirements (roughness<200 nm, oxide layer<5 nm) • 3rd version of the undulator intersection fabricated (2014.03) • Chemical polishing technique is developed for the U-chamber (for better quality control)


Thank you for your attention

Documents

Updated Status of the PAL-XFEL Vacuum System · PDF fileUpdated Status of the PAL-XFEL Vacuum System . April. 2, ... Special extrusion die . ... LVDT corrector. corrector