1. Update on out-gassing tests
2-May-06
A. Gonidec & V. Falaleev

2. Reminder: - 10-6 mbar vacuum needed in a decay volume to keep the
background to less than one fake even per year
- according to preliminary estimations the main gas load source
is outgassing of the decay (“blue”) tube and photon veto scintillator
- a pump choice depends not only on vacuum needed but also on gas
composition (mass spectrometry)
Blue tube
New test: - longer pumping time
- mass spectrometer measurements
Two methods of outgassing estimation:
- dynamic: when a stable vacuum is reached an outgassing load is
equal to pumping speed (unfortunately the pumping speed
and outlet conductance is not well know)
- static: when the pump is off the outgassing is the main reason of
a pressure rise
2-May-06
A. Gonidec & V. Falaleev

3. 2-May-06
A. Gonidec & V. Falaleev

4. Duration of pumping, days 10 15
Blue tube - results
2005 test
2006 test
Duration of pumping, days 10 15
Vacuum reached, mbar
3 ·10-5
6 · 10-6
Average outgassing, (mbar l)/(sec cm2)
1.6 · 10-9
4.5 · 10-10
High vacuum outgassing, (mbar l)/(sec cm2)
3 · 10-9
1.35 · 10-9
High vacuum outgassing load (mbar l)/sec
1 · 10-2
Worst (dynamic) outgassing, (mbar l)/(sec cm2)
6.5 · 10-9
Worst (dynamic) outgassing load, (mbar l)/sec
4.8 · 10-2
Mass spectrometer measurement shows that the main gas component is water.
2-May-06
A. Gonidec & V. Falaleev

5. New test: - smaller and better prepared vacuum tank
Scintillator
New test: - smaller and better prepared vacuum tank
- pure scintillator measurement
2005 test:
20 plates proto in big tank
2006 test:
2 plates in small tank
CKM
Number of days to reach stable pressure 25 14
5 days of pumping
Average outgassing, (mbar l)/(sec cm2)
7 ·10-10
1.3 · 10-9
6.7·10-9
Worst outgassing , (mbar l)/(sec cm2)
2 · 10-9
2-May-06
A. Gonidec & V. Falaleev

6. 2-May-06
A. Gonidec & V. Falaleev

7. Blue tube + Scintillator Blue tube Scintillator
“Reasonable” outgassing, (mbar l)/(sec cm2)
1.35 · 10-9
1.3 · 10-9
Worst case outgassing, (mbar l)/(sec cm2)
6.5 · 10-9
2 · 10-9
Surface, cm2
7.4 · 106
3.9 · 107
Reasonable case
Worst case
Blue tube outgassing load (mbar l)/sec
1 · 10-2
4.8 · 10-2
Scintillator outgassing load (mbar l)/sec
5.1 · 10-2
7.8 · 10-2
Total outgassing load (mbar l)/sec
6.1 · 10-2
12.6 · 10-2
Pump power needed to reach 1 · 10-6 mbar (100% conductance), l/sec
6.1 · 104
12.6 · 104
Reminder: 5 · 104 l/sec pumps are available on the market
2-May-06
A. Gonidec & V. Falaleev

8. Ongoing tests and planned work
Outgassing measurement of :
TYVEC
lead
spaghetti prototype
straws prototype
Mass spectrometer analysis
2-May-06
A. Gonidec & V. Falaleev