1. The need for more outgassing data of materials for accelerators and storage ring experiments
E. Hedlund
Uppsala University, Sweden
SP-Swedish Testing and Research Institute

2. Outline Outgassing properties of materials
Recommended practices for outgassing measurements
Measurement accuracy
Create a database for outgassing measurement
Outlook

3. 16th IUVSTA Workshop Outgassing properties of materials
Conclusions:
Better correlation between outgassing measurements and the morphology and chemical structure of the surface and near surface layers
Identification of the chemical state of H2O on or near the surface.
Measurement of the sticking coefficient of H2O on practical surfaces (steel and Al) as a function of surface conditions

4. Conclusions… Influence of deposited passivation layers of outgassing
Measurements and corresponding modeling of outgassing from model systems
Experiments that could identify and quantify the role of diffusion in the near-surface region of vacuum materials

5. From this we can conclude:
Lack of published outgassing data
Need for a freely available database with e.g. following parameters:
Precise material, surface and bulk treatments, surface structure, cleaning, heat treatment etc.

6. Outgassing methods Throughput method Conductance modulation method
Two-path method
Gas ackumulation method
Mass-loss measurements
”Recommended practices for measuring and
reporting outgassing data” by P. A. Redhead in
J. Vac. Sci. Technol. A 20(2002)

7. CHICSi

8. Outgassing methods
Method: pump down for a certain time and observe the final pressure.
Must know the pumping speed at the chamber, which gives larger uncertainty.

9. CHICSi
Problem to find data for conductive and non-conductive glue, printed circuit boards and insulators
NASA: Total Mass Loss (TML) Collected Volatile Condensable Material (CVCM)

10. Outgassing from glue H2 H2O CO CO2 CH4 rate 377 1.15 90 1.5 1.410-6
Type
Weight
Bake-out in air
Bake-out in vacuum H2
H2O CO
CO2
CH4
Total out-gassing rate
(g]
Temp(ºC ]
Time (h ]
Temp (ºC)
Time
(h)
(mbar l /s g)
rate
377
1.15 90
1.5
1.410-6
150 24
1.3
10-9
1.8
10-10
2.0 4
10-11
610-11
410-9
H20E
2.16
410-7
1.6
10-7
610-8
810-9
610-7 4
10-11
1.2 3 2
1.4
7 10-9
H27D
3.90
1.110-6
3 10-7

11. Printed circuit boards
Kapton
Ceramics
FR-4
Glass reinforced kapton
Kapton insulated band cable

12. Outgassing from printed circuit boards
Materials
Area
Bake-out H
H2O CO
Total outgassing rate
cm2
Air ºC
Time h
Vacuum ºC
Time h
mbar l/
cm2s
Pyralux (2 layers) 19
150 20
210-8
410-10
310-9
310-8
AP (2 layers) 98
210-10
410-11
310-10
110-9
Epoxy-Acrylic (2 layers) 30
110-10
Epoxy-Glass fibre, 1 layer 36
210-9
Alumina (14 layer electrical print) 32
3·10-10
Glass reinforced Kapton 74 24
210-11
FR4 (4 layers)
475
1.510-11
FR4
331
610-10 23
210-13
610-11 77
410-12
FR4 – 6 layers
120
<110-10
510-10

13. Outlook
Increase bakeout temperature for the whole system to 200 ˚C or possibly 300 ˚C.
Search for conductive and non-conductive glue with lower outgassing rate
Find a new type of a flexible multi-layer bandcable

14. Outgassing metrology Round robin study of outgassing:
- materials from same batch,
- same surface treatment
- run at experimental facilities in
different laboratories
Create a database (only UHV?)