Status and plan for X-band high field experiments at KEK

US High Gradient Collaboration WorkshopUniversity of Maryland

Jan. 23-24, 2008

KEKT. Higo

Contents

• KEK road map• Plans of X-band activities• Collaborations with SLAC and CERN• Nextef commissioning• NWG on-going test• Surface creation for basic high-gradient studies• Structure fabrications• Conclusion

X-band strategy• X-band activity is not explicitly written in the road

map. However,• We understand

– the accelerator laboratory and KEK DG support the study for high gradient, at least spiritually,

– but also hopefully with some budgetary support JFY08

• KEK is progressing to engage – MoU between SLAC and KEK on advanced accelerato

r research including high gradient study, provably under US-Japan collaboration framework.

– Agreement of collaboration between CERN and KEK including high gradient study.

Gross plan of X-band activity at KEK

2006 2007 2008 2009 2010

Trial fabrication

Low power test

Feasib

ilit

y o

f C

LIC

sch

em

e

Narrow waveguide 　

SLAC short-cell stack

High power / high field experiment at New XTFHigh power testGLC acc

structure　

CLIC equivalent, acc structure　

Basic structure　

・・・　 CLIC acc structure　・・・　

Design electrical and mechanical

Fabrication of actual acc

structure

Fabrication of CLIC equivalent. acc structure

High power test at SLAC and CERN

We are basically along the same plan as this, but probably taking a little more time, extending beyond 2010.

(Taken from presentation by Matsumoto in the last workshop last June)

Nextef progressEstablishing power generation and transport in 2007

Nextef inside shield roommost basic components are now in line.

Nextef components in shield roomSLAC 3dB

60cm KX03 structure

Lounine Load(based on SLAC design)

Ohtsuka Load

Guard window TE01-type

IP 30l/s

WR90

DC made by BINP

Nextef commissioning in 2007

• Independent Klystron operation in Sep.

• Two-klystron operation in Oct.

• Power feeding to structure in Nov.-Dec.

• Skip structure and establishing high power capability in Jan. ‘08

• Now 24 hr/d running (during linac operation) at ~20MW, 50ns, 50Hz level.

Now increasing the system powerafter back to skipping structure

RF Pulse shapesAutomatic control by seeing VAC level

Trend of RF power and VAC levelThe very basic features are now working. We need sophistication of the system and establishment of high power level.

Nextef near future plan

Various detection tools are to be integrated into Nextef control system

System control PCPython, Linux

TDS3034B (300MHz)TDS3054B (500MHz)

DPO7104(1GHz)

VME Acoustic (SLAC)

Mod. PLC

Acc PLC

CCG

RF crystal

Various signal

CT

FCAM

Data storageKEKB Inj. control

DL7480(500MHz)

History 4MW/ch

Modulator

KlystronLLRF

FPGA (100MHz)

S/H & DC Amp

Discri

Acoustic

INTLK Safety

X-ray

Etc.

Etc. Etc.

Etc.

X-ray

Yet to be implemented

Future problem: Time / area sharing in Nextef

among X + C + S?• For a C-band RF unit preparation

– Two acc. structures are tested at the same area as Nextef in 2009 spring-summer.

– Though probably Super KEKB will not use C-band for energy exchange.

• S-band acc. structure processing– When needed for e+ area usage, we should do it.

• We may need to operate the C-band (and S-band in principle) setup in “Nextef” area for three months or so in 2009!?

• Best is to expand the area under management-level decision.

Basic high field study with narrow waveguide (NWG)

• Started study at GLCTA– Cu-002 (first copper) in 2006

• Restarted at klystron assembly hall in 2007– Cu-002

• Baking troubles in a new setup• Tested, cut and inspected, • Cu-004 study copper again in an established setup

– SUS-003 (first SUS) tested• Troubles in baking again but studied up to the max available

power level• Tried BD rate evaluation, but found it difficult

• We want further to– Test the same sample in a different places to compare criteria

of processing and breakdown– Refrain study one made in the same manner to get variations

and statistics.

Surface field at 100MW power flowhigh magnetic field in addition to high electric field

Type Width Height

vg/c Ey Hx Ey / Hx

mm mm % MV/m kA/m

WR90(standard)

22.86 10.12 82 28 61 460

SLAC high magnetic field

(low impedance)22.86 1.3 82 79 171 460

SLAC low magnetic field

(high impedance)13.33 10.12 18 80 37 2137

KEK Narrow waveguide

(actual HFSS)14 1 35

176(150-

215)

163(???)

1080(???)

NWG test setup and some result

Baking 2nd one (out of three times)

NWG setup with a klystron

Effect of baking at 200 degCwith leakage trouble!?

Installation in April after Cu-002Baking at 200 C vac leakage two times (at low temp)Processing moderately (!?) Suffered from Modulator inverter power supply Klystron pulse shortening TE01 guard window acivityBut almost reached the system power limit ~ 50MWNow remove SUS-003 and start processing the system again toward higher power level.

Processing and identification of event

Program controlled processing By seeing VAC level INTLK with increase of RF reflection, light from window, etcOscilloscope view taken as a pictureAnalyze with RF shapes and X-rays.

Klystron pulse shortening

Breakdown at narrow waveguide triggered by NWG discharge?

Power

VAC Klystron Output

RF reflect Light from GW

Transmitted RF

Evaluation of high field performance

Calibration of power and the method of evaluation of high field are under way.We want to compare this result to other experiments.

Power level to be recalibrated.

Rate evaluated during four hours.

Why limited at so low field level

• Due to large magnetic field?– 108 degC rise at 400ns with 50MW– Comparing to copper with 30 times less rise

• Large power density?• Material preparation?• Processing criteria?

– Slow ramping with keeping good vacuum ~10-6 Pa

Do copper study again

Materials preparation for basic studies on E and H field

• Higashi has been collaborating with Dolgashev of SLAC– Test in SW and TW in a-cell or three-cell setup– Test of magnetic field in TE01 mode cavity– Materials and surface preparation

• Copper, Moly, • OFC, 6N, single crystal, …• Rinsing method• Baking in a close volume until just before installation to high

power setup

• We want to proceed this-type of study also at KEK. – Which shield room? Not yet determined.

SLAC chemical etching procedure

Frontier Cleaner A02 + Megasonic (3 min x 3 time)

Ultra-purer water + Megasonic (5 min)

IP (50degC, 5min)

Diffusion bonding + Brazing (Structure completed)

Frontier Cleaner A02 + Megasonic (3 min x 3 time

Ultra-purer water + Megasonic (5 min)

IP (50degC, 5min)

Baking (300-500 degC, 5days)

Purged N2

Shipping to SLAC and installation in high power test stand

Semiconductor rinsing technologies

Pulse heating (TE01) test sample

Designed by G. Bowden

76.0 +/- 0.05

67.46

6.0 +/- 0.05

7.2

4.32

4.24

Drill through 6 holes EQ spaced

Defects (dislocation, hole, impurity): scattering of conduction-band electron makes non-vector field 　　 Electrical conductivity?

Stress due to dislocation: not continual body of elastical material.

What happens with annealed 6N copper? What about HIP copper?

What about single crystal 100-face copper (100)?

Single crystal

Pulse Heating Test Samples

6N copper, Single crystal(100)Finished by Diamond Tuning

Surface conditions

• As received

• 800 degC. 3days annealing

• HIP

• HIP + Chemical Etching

Fabrication of structures for high gradient study

• Target– Extend SLAC/KEK X-band legacy to recent CLIC approach.

• Framework– Electrical design by CERN– Mechanical design and fabrication by KEK and SLAC– Assembly and tuning at SLAC and/or KEK– High power rest at SLAC and KEK until CERN stand-alone

system is established• Three CLIC_VG1 in collaboration with CERN and SLAC

– T18_VG2.4_Disk– Assembly and testing are being done by SLAC and KEK– These structures serve as a cross referencing.

• Quadrant-type CLIC structure– T18D_VG2.4_Quad– Pilot study was done with five vendors.– We plan to proceed a structure fabrication by next summer.

Disk based structure: fabrication in the same manner

as previous SLAC/KE X-band collaboration for GLC

Bead pull by KEKChemical treatment and bonding by SLAC

Parts fab. by KEK and ship to SLAC

Quadrant: fabrication of short test parts and measurement by ZEISS CMM at KEK

Obtained reasonable quality to proceed to full quadrant test fabrication

Item / Present / Next program

• Local profile shape control: OK with deviation from design within specified 2.5 microns.

• Absolute profile shape : Positioning is to be studied in a full-size fabrication study.

• Roughness: Ra ~ 0.2 – 0.4 micron. improvement to Ra~0.1 micron within a reasonable cutting time is to be studied.

• Edge treatment: Burr within a few 10 microns level. 50-micron radius is to be studied.

• Other high field related issues?:

Local profile shape within +-2.5 microns from design (Case: U-corp)

Surface roughness (Case: U-corp)

Present Ra ~ 0.2—0.4 micron To be studied in actual full-size fabrication: whether to reach specified Ra~0.1 micron

Spurs with carbide tool (case of YADSA)

21

3

Conclusion • Nextef hardwares are now ready. System high power o

peration is ongoing. • Additional sophisticated measurement tools are to be e

stablished.• A series of tests of CLIC-directed structures will be from

coming March.

• We continue basic studies on high gradient with varying surface treatment and material.

• Formal collaboration frameworks are being established with CERN and SLAC.

• Through proceeding the above actions, high gradient X-band activities in KEK will be more formally acknowledged.