Tetsuo ABE - CERN Indico

Status of

Quadrant-type Waveguide-

damped Structure Fabrication

and Single-Cell SW Cavity Test

Tetsuo ABE<[email protected]>

High Energy Accelerator Research Organization (KEK), Japan

CLIC Workshop 2019 @ CERN

2019-01-21

Tetsuo ABE (KEK)

Contents

1. Status of Quadrant-type Waveguide-damped Structure (TD24_QUAD) Fabrication

2. Status of Single-Cell SW Cavity Test

CLIC Workshop 2019 (2019-01-21) 2

Tetsuo ABE (KEK) 3CLIC Workshop 2019 (2019-01-21)


Disk-type v.s. Quadrant(or Half)-type

Advantages

Machining by turning

Very smooth surface (Ra = ~30 nm)

Shallow machining damage (< 1 mm)

Disadvantages

Ultra-high-precision machining of dozen of disks

→Stack and bonding

Great care needed

Surface currents flow across disk-to-disk junctions.

Disk-type Quadrant-type

Advantages

Surface currents do not flow across any bonding junction.

Simple machining by five-axes milling machines

Simple assembly process

Possibility of significant cost reduction

Disadvantages

Not very smooth surface (Ra = ~ 0.5 μm)

Deep machining damage (10 - 20 mm)

Virtual leak from quadrant-to-quadrant junctions

Field enhancements at the corners of quadrants

Tetsuo ABE (KEK) 5

Design improvement

CLIC Workshop 2019 (2019-01-21)

FlatContact

Quadrant A

Quadrant B

8×R50μm

Large R(8×R0.4mm)

Small Gap(0.1mm)

Old Design( Bad performance)

Improved Design

Avoid virtual leak Suppress the field enhancement

The chamfer radius and small-gap size were optimized based on simulation to minimize

A) Field enhancement at the corner of the quadrants ( +25%)

B) Deterioration of the shunt impedance ( -2%)

For details, see T. Abe et al., “Fabrication of Quadrant-Type X-Band Single-Cell Structure used for High Gradient Tests,”

presented at the 11th Annual Meeting of Particle Accelerator Society of Japan (2014), Paper ID: SUP042.

to

http://www.pasj.jp/web_publish/pasj2014/proceedings/PDF/SUP0/SUP042.pdf

Tetsuo ABE (KEK) 6

Demonstration of the High-Gradient Performancewith a single-cell SW cavity

CLIC Workshop 2019 (2019-01-21)

Good high-gradient performance demonstratedMulti-cell traveling structure

T. Abe et al., "High-Gradient Test Results on a Quadrant-Type X-Band Single-Cell Structure,“presented at the 14th Annual Meeting of Particle Accelerator Society of Japan (2017), PaperID: WEP039.

(SW: Standing Wave)

Cycle Operation

https://lib-extopc.kek.jp/preprints/PDF/2017/1727/1727038.pdf

https://lib-extopc.kek.jp/preprints/PDF/2017/1727/1727038.pdf


Postmortem of SD1_QUAD-R04G01_K1

Almost no damage in the 0.1-mm gap!

The small 0.1-mm gap successful!

BD spots aligned!


Currently fabricating “TD24R10_QUAD-R04G01”Round chamfer: 0.4 mm

Gap between quadrants: 0.1 mm

Based on the improved quadrant design

http://www.pasj.jp/web_publish/pasj2014/proceedings/PDF/SUP0/SUP042.pdf


Cavity Design based on CLIC-G*Made by Jiayang Liu (THU) and Alexej Grudiev (CERN)

Tetsuo ABE (KEK) 10

From the Cavity Design to the 3D Mechanical Drawing

CLIC Workshop 2019 (2019-01-21)

minus

Tetsuo ABE (KEK) 11

A Quadrant Machined with Ultraprecision Milling

CLIC Workshop 2019 (2019-01-21)

By U-Corporation

Tetsuo ABE (KEK) 12

RF Measurement before EBW (1/3)

CLIC Workshop 2019 (2019-01-21)

With the four quadrants clamped (EBW: Electron-Beam Welding)


RF Measurement before EBW (2/3) Measured by T. Takatomi and T. Abe

IN

Tetsuo ABE (KEK) 14

RF Measurement before EBW (3/3)

CLIC Workshop 2019 (2019-01-21)

11.4084 GHz (vac) 11.4074 GHz (vac&30degC)

~10 MHz increaseExpected through EBW

Measured by T. Takatomi and T. Abe

Tetsuo ABE (KEK) 15

EBW on the side surfaces

CLIC Workshop 2019 (2019-01-21)

By TAIYO EB tech

Tetsuo ABE (KEK) 16

Four Quadrants Bonded with the EBW

CLIC Workshop 2019 (2019-01-21)

(EBW: Electron-Beam Welding)

Tetsuo ABE (KEK) 17

RF Measurement after the EBW

CLIC Workshop 2019 (2019-01-21)

IN OUT

Measured by T. Takatomi and T. Abe

Tetsuo ABE (KEK) 18

Before and after the the EBW

CLIC Workshop 2019 (2019-01-21)

EBW

The end cell and its neighboring cells significantly deformed

Tetsuo ABE (KEK) 19

Before and after the EBW

CLIC Workshop 2019 (2019-01-21)

11.4074 (vac&30degC)

11.4099 GHz (vac&30degC)

EBW

+2.5 MHz

(We expected ~10 MHz increase by the EBW.)

Tetsuo ABE (KEK) 20

Change in Transverse Size Measured using a CMM(Carl Zeiss UPMC 850 CARAT)

CLIC Workshop 2019 (2019-01-21)

Quad_No.1

Quad_No.2 Quad_No.3

Quad_No.4

-15.000

-10.000

-5.000

0.000

5.000

10.000

15.000

0 50 100 150 200 250Size

ch

ange

(af

ter –

be

fore

) [u

m]

Position along the beam axis [mm]

No.2 - No.3 No.1 - No.4 No.2 - No.1 No.3 - No.4

By T. Takatomi (KEK / Mechanical Engineering Center)

Average size change: +1.5 mm The quadrants largely deformed

around the end cell

Expansion

Shrinkage

IN OUT

Tetsuo ABE (KEK) 21

After brazing tuner pins…

CLIC Workshop 2019 (2019-01-21)

Most of the tuner pins dropped!

Pearskin!

OFC (class1)CuZr

First time to be processed at a high temperature

Alumina ceramics put here

High-temperature-treated copper plates made of CuZr and pure copper (OFC, class1)

Tetsuo ABE (KEK) 22

Longitudinal Size Measurement after the Final Machining

CLIC Workshop 2019 (2019-01-21)

-0.01

0

0.01

0.02

0.03

0.04

d1 d3 d5 d7 d9 d11 d13 d15 d17 d19 d21 d23 d25De

sign

–M

eas

. [

mm

]

Iris No.

Quad_No.1

-0.03

-0.02

-0.01

0

0.01

0.02


sign

–M

eas

. [m

m]

Iris No.

Quad_No.2

-0.02

-0.01

0

0.01

0.02

0.03


sign

–M

eas

. [m

m]

Iris No.

Quad_No.3

-0.03

-0.02

-0.01

0

0.01

0.02


sign

–M

eas

. [m

m]

Iris No.

Quad_No.4 Iris-center positions accurate (+- 5 mm) Iris thicknesses depend on iris numbers.

Signs of the slopes different between No.1,3 and No.2,4

Iris-center position

Iris thickness

Assuming different hardness between No.1,3 and No.2,4,the difference in the slope sign originates from the difference in wear volume on the ball end mills.


Quad_No.1

Quad_No.2

Quad_No.3 Quad_No.4

Softer

Harder

Harder

Softer

Tetsuo ABE (KEK)

Updated Schedule on TD24_QUAD

① Milling of quadrants to be completed by March 2019

② RF & size meas. EBW RF & size meas. by April 2019

③ Brazing of tuner pins, couplers, etc. by May 2019

④ High-gradient test to be started before summer 2019

CLIC Workshop 2019 (2019-01-21) 24

Tetsuo ABE (KEK) 26

DUT: SLAC Full-Choke Cavity

CLIC Workshop 2019 (2019-01-21)

Valery Dolgashev (SLAC)

An example of breakdown image

High-power RF conditioning doneby Valery Dolgashevup to Eacc = ~150 MV/m

(During the RF measurement in KEK)

(For details, see SLAC-PUB-15145 )

T. Abe

http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-15145.pdf

Tetsuo ABE (KEK) 27

Fields in Full-Choke cavity,normalized to 10 MW of input power

CLIC Workshop 2019 (2019-01-21)

Normalized on-axis fields

10 20 30 40 50 60 700.0

0.2

0.4

0.6

0.8

1.0

z mm

No

rma

lize

dA

mp

l.

20 40 60 800

50

100

150

200

250

300

z mm

Ez

MV

m

On axis electric field normalized to 10 MW of input power

V. Dolgashev

Measurements Calculations (tuned to match the mesa.)

Tetsuo ABE (KEK) 28

Fields in Full-Choke cavity,normalized go 10 MW of wall losses

CLIC Workshop 2019 (2019-01-21)

Surface electric field,Emax = 319 MV/m

Surface magnetic fieldHmax = 526 kA/m

Surface Poynting vectorPmax = 5.7x1013 W/m2

V. Dolgashev

Tetsuo ABE (KEK) 29

Motivation

CLIC Workshop 2019 (2019-01-21)

Results of single-cell cavity tests by SLAC

BDR determined byMaterial hardness?Thermal stress?

Tetsuo ABE (KEK) 30

High-Power Pulsed Laser

CLIC Workshop 2019 (2019-01-21)

Sketch of Valery Dolgashev (SLAC) showing his idea

RF and laser pulses are independent thermally.Additional metal fatigue accumulate BDR increase ?

Full-choke cavity

Laser power sensor

The real systemM. Yoshida and T. Abe made

inside Nextef/Shield-B

Green laser (532 nm) with 20 ns, ~10 mJ max

Dump

Independent vacuum chamber containing a copper coupon for irradiation tests (Y. Higashi made)

Longpassmirror

Beam splitter

Focus lens

To make local thermal stress

Tetsuo ABE (KEK) 31

Laser Power-Density Calibration based on Ablation Threshold

CLIC Workshop 2019 (2019-01-21)

Notch filter

Linear manipulator

TV camera

Copper coupon

Full-coke cavity

Tetsuo ABE (KEK) 32

Laser Power-Density Calibration based on Ablation Threshold

CLIC Workshop 2019 (2019-01-21)

1st irradiation on Point A2nd irradiation on Point A1st irradiation on Point B2nd irradiation on Point B

1st irradiation on Point A

The arrows indicate the laser energy at which the light emission started in the video.

Valery Dolgashev predicted that there should be a clear threshold in the vacuum-pressure response, which corresponds to the ablation threshold.

The spectrum of the emitted

light will be measured by

using a hyperspectral

camera.

A clear thresholdobserved!

(with prelim. calib.)

Click here to start this video!

Recorded by T. Abe

Green laser


SEM images by Chris Pearson (SLAC)

1 mm

SEM images show pulse heating damage from the green laser.Normal surface

1 mm

Tetsuo ABE (KEK)

Summary TD24_QUAD status The fabrication had been successful until the EBW. Two of the four quadrants turned out not to be pure copper after the first high-temperature

process of brazing. Most probably CuZr

We have decided to started over; need additional several months. High-gradient test to be started before summer 2019

Full-choke single-cell cavity test with laser Everything just ready for high-gradient test, including the high-power pulsed laser system Compare BDRs with or without the laser irradiation for various irradiation positions

Other single-cell test cavities Two TD24-based damped cavities (with the disks brazed or diffusion-bonded) waiting to be tested Undamped cavities made of large-grain copper

34CLIC Workshop 2019 (2019-01-21)

(EBW: Electron-Beam Welding)


Thank you for your

attention!


Backup Slides

Tetsuo ABE (KEK) 37

Fields in Full-Choke cavity,normalized to 10 MW of input power

CLIC Workshop 2019 (2019-01-21)

Surface electric field, Emax = 309 MV/m Surface electric field, Hmax = 510 MV/m

11.30 11.35 11.40 11.4520

15

10

5

0

f GHz

S2

2

11.410 11.412 11.414 11.416 11.418 11.420

14

12

10

8

6

4

2

f GHz

S2

2

Measured (Blue) and calculated S11 (Red), 0.15 dB losses added to calculated S11., S11_HFSS= 0.24774

Qloaded = 4516.46beta= 1.659, Qo = 12009

|S1

1|

|S1

1|

0 p/2 p p mode

V. Dolgashev

Tetsuo ABE (KEK) 38

Parameters of periodic structures

CLIC Workshop 2019 (2019-01-21)

Name A2.75-T2.0-Cu A3.75-T1.66-Cu A3.75-T2.6-CuA3.75-T2.6

FullChoke-Cu

A5.65-T4.6-Choke-Cu

A5.65-T4.6-Cu T53VG3

Stored Energy [J] 0.153 0.189 0.189 0.471 0.333 0.298 0.09

Q-value 8.59E+03 8.82E+03 8.56E+03 13.5E+3 7.53E+03 8.38E+03 6.77E+03

Shunt Impedance [MOhm/m] 102.891 85.189 82.598 52.4 41.34 51.359 91.772

Max. Mag. Field [A/m] 2.90E+05 3.14E+05 3.25E+05 3.22E+5 4.20E+05 4.18E+05 2.75E+05

Max. Electric Field [MV/m] 203.1 268.3 202.9 203.3 212 211.4 217.5

Losses in a cell [MW] 1.275 1.54 1.588 2.501 3.173 2.554 0.953

a [mm] 2.75 3.75 3.75 3.75 5.65 5.65 3.885

a/lambda 0.105 0.143 0.143 0.143 0.215 0.215 0.148

Hmax*Z0/Eacc 1.093 1.181 1.224 1.215 1.581 1.575 1.035

t [mm] 2 1.664 2.6 2.6 4.6 4.6 1.66

Iris ellipticity 1.385 0.998 1.692 1.692 1.478 1.478 1

Peak Poynting vector [W/um^2] 21.4

V. Dolgashev


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