CLIC09 WG4 RF Structure 1

Engineering Perspectives on Quadrants (2)

CLIC09 Workshop

KEKY.Higashi

CLIC09 WG4 RF Structure 2

Contents

1. Dark current characteristics on the KEK quadrants structure experiment

2. Surface treatment for dark current/EFE mitigation

3. Material

4. FANUC Co. fabrication method proposal (tentative)

5. Assembly envelopments

CLIC09 WG4 RF Structure 3

Notice: Deformed cavity wall

Cell 3(×35）

Cell 3(×100）

Cell3 deformation： 0.053mm

32009/10/12

KEK’s version: 50 micron chamfer

Roughness: ~ 5 micron order?

CLIC09 WG4 RF Structure 4

QMS (1) :RF Power and gasesPressure of H2 dominated. Pressure of water is inactive.

21828

44

RF Power into Acc

ACC Chamber CCG

10-8

10-7

10-6

10-5

0.0001

Pre

ssure

(Pa)

Dark current characteristics on the KEK quadrants structure

~x1000 higher than T18 structure -> Detail is talk　 by Higo

CLIC09 WG4 RF Structure 5

Enhanced Field Emission/Dark current(Reference :J. Wang, G. loew)

These can be classified into various categories;

(a) Metallic surface roughness due to imperfect machining, scratches, micro protrusions, “tip-on-tip” productions

(b) Metallic dust, micro particles

(c) Grain boundaries

(d) Molten craters after breakdown

(e) Dielectric impurities and layers

(f) Absorbed gas

(g) Metal-insulator-vacuum (MIV) or metal-insulator-metal (MIM) layers

CLIC09 WG4 RF Structure 6

Surface treatment for dark current/EFE mitigation

-5 10-7

0

5 10-7

1 10-6

1.5 10-6

0

200

400

600

800

1000

0 2000 4000 6000 8000 1 104 1.2 104

etchingdaiamond1High press1Vacuum1oil-less1Hydrogen1

Temperature C)( ﾟ

Time (s)

Out gas characteristics on various treatment of OFC

CLIC09 WG4 RF Structure 7

Field Emission Microscope

-210-6

-110-6

0

110-6

210-6-210-6

-110-6

0

110-6

210-6

051071108

1.5 108210

8

-210-6

-110-6

0

110-6

210-6

50nm

nAPotential: 20V, Resistance: 100 Ohm

0

5 105

1 106

1.5 106

0 2 107

4 107

6 107

8 107

1 108

1.2 108

Calcuration of field emission090908

Current density(A)

V/m

Check Grain boundaries, impurity, material defect, roughness

CLIC09 WG4 RF Structure 8

Ultra High-Precision Diamond Tuning Surface of Copper

Class1

60mm Diameter, 6mm thickness

Contacted region

Inner diameter 35mm

PV: 21nm PV: 13nm

Enough quality as metal-metal contact for Quadrants?

CLIC09 WG4 RF Structure 9

Roughness: 3.3nm (PV)

Field enhancement occurs?

CLIC09 WG4 RF Structure 10

Leak rate: < 1.7e-11Pal/secIP (Semicon grade) Rinse (50degC)

Degreasing

Assembly: Class 100

No vacuum leak was found

CLIC09 WG4 RF Structure 11

Surface Treatment for Quadrants • Pre-machining (remain 100 m)• 650 degC annealing• Final machining (same surface roughness to dis

k)• Chemical Etching (~5 m)• HPWR (remove burs, particle)• Degreasing (remove particle and fine oxide laye

r)• 150~200 degC baking in vacuum• Assembly in the ILC grade clean room

CLIC09 WG4 RF Structure 12

Material

Should be Considered High Gradient Test Results of Single Cell SW Structures

CLIC09 WG4 RF Structure 13

FANUC Co. fabrication method proposal (tentative)

45°

230mm

CLIC09 WG4 RF Structure 14

Cost Estimation (very rough)TD18 structure Unit is MYen

Disk Type Quadrants

Material

Whole fabrication 2.5 2.8

Vacuum chamber - 1.0

Surface treatment 0.5 0.3

Bonding (Assembly) 1.5 0.5

RF Tuning 0 (eventually) 0 (eventually)

Absorber

Baking 0.5 0.5

Instauration

Alignment

Total

?

CLIC09 WG4 RF Structure 15

Summary

1.One order more precise machining (roughness, dimension) technologies glowed up compare to NLC/GLC generation, So Quadrants is very attractive

2. 5000~7000 disks, 25~30 structures fabricated for NLC/GLC

3. In order to understand fabrication technologies for high gradient quadrants structures, may be needed 2~3 years

CLIC09 WG4 RF Structure 16

CLIC09 WG4 RF Structure 17