Copper Treatment for Single C T t t f Si l Cell SW structure - - PowerPoint PPT Presentation

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Copper Treatment for Single C T t t f Si l Cell SW structure - - PowerPoint PPT Presentation

Oct 03, 2022 290 likes •579 views

Copper Treatment for Single C T t t f Si l Cell SW structure Cell SW structure 2 nd International Collaboration Meeting on X Band Accelerating Structure on X-Band Accelerating Structure 080514 KEK/SLAC KEK/SLAC Y.Higashi, T.Higo,

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SLIDE 1

C T t t f Si l Copper Treatment for Single Cell SW structure Cell SW structure

2nd International Collaboration Meeting

  • n X Band Accelerating Structure
  • n X-Band Accelerating Structure

080514

KEK/SLAC KEK/SLAC

Y.Higashi, T.Higo, K.Yokoyama V.Dolgashev, S.Tantawi

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SLIDE 2

Field Emission and RF Breakdown in High- Field Emission and RF Breakdown in High- Gradient Room-Temperature Linac Structure

  • J. W. Wang and G. A. Loew

SLAC-PUB-7685 October 1997 Pulse rf breakdown studies

  • L. Laurent, G. Caryotakis, G. Scheitrum, D.

Sprehn, N. C. Luhmann, Jr SLAC PUB 8409 SLAC-PUB-8409 March 2000

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SLIDE 3

Purpose

To find statistically high gradient limit for y g g copper materials by experiments

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SLIDE 4

Who decide high gradient threshold ?

Magnetic field ?

F ti k l ti d i t t d t l Fatigue crack nucleation and micro structure due to pulse heating

Electric field ?

Dark current ( β of F-N plot)

Surface contaminations/ Crystal defects ?

Dust, Copper oxide on surface

Vacuum level ? Hardness, degradation and purity of material ? Stored energy ?

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SLIDE 5

Cyclic stress-strain Cyclic stress strain

ref: ASM Handbook

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SLIDE 6

Cyclic stress-strain

ref: ASM Handbook

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SLIDE 7

Evolution of fatigue slip b d bands

N=4x103 cycling N=104 N=104

5

N=105

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SLIDE 8

Fatigue slip band on the surface of cycled copper

ref: ASM Handbook

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SLIDE 9

Mechanism of Microcrack Nucleation

ref: ASM Handbook ref: ASM Handbook

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SLIDE 10

First electron microscope pictures

  • f
  • f

1C-SW-A5.65-T4.6-Cu-KEK-#2

20 March 2008

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SLIDE 11

Grain boundary on iris of high-gradient cell

Grain boundary in high electric field area Grain boundary in high magnetic field area

Lisa Laurent, 20 March 2008

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SLIDE 12

Cracks between grains and deformation of the grain on outside wall of high gradient cell θ γ12 γ12 γ12 γ12 γ11=2γ12cos(θ/2)

Lisa Laurent, 20 March 2008

γ11

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SLIDE 13

Scattering of conductive electrons due to grain b d d di l ti ( l ti ) boundary and dislocation (speculation)

Mean free pass of conductive Mean free pass of conductive electron 55.6 nm (Ideal crystal) t=4x10-14 sec = 40 fsec Crystal defect J=σE Electric resistance σ RF Long pulse Temp.

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SLIDE 14

Mechanical Design

WC150 ss Conflat flanges Cu

Sample Dimensions

copper plug temperature sensor

  • G. Bowden
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SLIDE 15

Stylus profilometer data and normalized pulse heating temperature,

1 3 24

pulse heating experiment, first copper sample

0 9 1 1.1 1.2 1.3 16 18 20 22 24

ture

Temperature

0 5 0.6 0.7 0.8 0.9 8 10 12 14 16

alized temperat Height [um]

0 1 0.2 0.3 0.4 0.5 2 4 6 8

Norma H

Profilometer

2.5 2.25 2 1.75 1.5 1.25 1 0.75 0.5 0.25 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 0.1 2

Radius [cm]

Profilometer Profilometer data – Lisa Laurent 11 October 2007

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SLIDE 16

Pulse Heating samples g p

  • 1. OFC-class1 As machined

SLAC t hi SLAC etching H2 treated (1000deg.C) Vacuum baking (600deg.C)

  • 2. 6N-Copper As machined

HIP (900deg.C/1000kg/cm2) H2 treated (1000deg.C) Vacuum baking (600deg.C)

  • 3. Single crystal Copper (100)

φ50mm/1mm thick

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SLIDE 17

Related Literature (1)

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SLIDE 18

Field Emission Dark Current Field Emission Dark Current

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SLIDE 19

Related Literature (1)

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SLIDE 20

Related Literature (2) Related Literature (2)

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SLIDE 21

Instead of HPWR Techniques Instead of HPWR Techniques

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SLIDE 22

Wet Cleaning tech. for Si Wafer was developed by RCA Co Ltd developed by RCA Co. Ltd,

  • Solvent

Cleaning Re-contaminant Solvent Cleaning Re contaminant

  • H2SO4/H2O2 (SPM) Organic, metals particles
  • NH4OH/H2O2/H2O (APM) particles, organic metals

HCl/H O /H O (HPM) t l ti l

  • HCl/H2O2/H2O (HPM) metals particles
  • HF/H2O (DHF) oxide film, metals Cu, particles

Needs 2-3 steps cleaning Needs 2 3 steps cleaning One step cleaning + megasonic

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SLIDE 23

S f t ti l t l Surface potential control

  • ζ potential
  • Particles
  • - - - - - - - - - - - - -
  • Copper surface
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SLIDE 24

Thermal Desorption Analysis

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SLIDE 25

Measurement of Low-energy electron emission from copper surface (Work Function change due to surface treatment) ( g )

Violet lamp

Monochro metor

Controller

PC

XY stage

Sample Counter

Class 1 6N S.C (110) As machined WF=4.78eV 4.89 4.99 HPWR WF=5.16eV 5.06 5.17

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SLIDE 26

My conclusion of the best treatment y

  • Copper material

Copper material Single crystal or large grain or amorphous

  • Without rf tuning or extremely small
  • Without rf tuning or extremely small
  • 1~2 µm etching

Ri i i Si f i i l ti

  • Rising using Si wafer rising solution
  • 900deg.C baking

8

  • <10-8 Pa vacuum (long mean free pass)
  • High shunt impedance cavity
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SLIDE 27

Trial of a new surface cleaning procedure

SLAC chemical etching 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 Frontier Cleaner A02 + Megasonic (3 min x 3 time Ultra-purer water + Megasonic (5 min) IP (50degC, 5min) Baking (300-500 degC, 5days) Baking (300 500 degC, 5days) Purged N2 Shipping to SLAC and instauration in high power test stand