Today we mounted the far aperture used to control the far iris. No problems were encountered with this.
We mounted the target ladder with the following configuration, see also pictures 1 and 2:
| Target # |
Target |
| I |
Blank 3mm |
| II |
Blank 10mm |
| III |
CH2 XV |
| IV |
CH2 XVIII |
| V |
natC 3 |
| VI |
- |
| VII |
Alpha Source |
The alpha source is 241Am + 239Pu
We also have mounted the near and far S2's with 12um mylar, and the pin diode with 0.9um mylar.
We only had the far iris arm actuator mounted, because a new iris arm for the near iris mount was being manufactured in the CIRCE workshop.
During ~midday through the early afternoon we found vacuum problems. These were solved by remounting the far chamber lid, and also remounting the far iris arm actuator (This had incorrect length bolts).
The new iris arm for the near S2 came back from the workshop, unfortunately we still could not mount it. We decided against mounting this iris arm, and instead mount the near S2 with the iris completely open and the 12um mylar protective foil.
We will only be able to measure at Elab = 4MeV, becasue at Elab = 6MeV the 7Li penetrates through 12um mylar and so we would be risking the near S2 during beam tuning (not an option!).
We mounted the near S2 with iris open and 12um mylar foil. The far S2 was already mounted with 12um foil and the iris arm aperture. The far S2 iris was opened fully (setting 1.5mm on actuator) ready for pumping and alpha source measurement.
At 16:50 we started the Ecodry 1 and 2 pumps and opened the manual gate valve. By 16:55 we fully opened the gate valve and also the T1600 backing valve, allowing both ecodrys to pump on the chamber. We then switched on the turbos.
By 17:20 the pressures read (in mBar):
- TPU1 = 3.4e-5
- TPU2 = 3.3e-6
- TPD1 = 3.4e-6
- TPD2 = 4.1e-6
- CHUP = 1.2e-5
- CHDW = 2.8e-5
During pump down we mounted the preamp boxes with daisy chained BNC cables.
We applied preamp power, correct currents drawn: ~1.5A for +ve and ~500mA for -ve
Far S2 biased to -130V, leak I = 1.46uA. Near S2 biased to -130V, leak I = 2.48uA.
Checking for noise, we see the following RMS noise in the RAL amps:
| RAL # |
RMS noise [mV] |
| I, II, XI |
~25 |
| IV |
~10 |
| V, VI |
~15 |
| X, XII, XIII, R S, Q |
~15
|
Diode biased to -70V, leak I = 0.02uA
We tested for ground loops - no obvious loops found for either S2 preamp
We connected the RAL amps to the FAIR DAQ, and started an alpha source run with pulser. The dead time was excessively high, ~90%
We started adjusting RAL thresholds up to RAL S, then we called it a day.
The Far S2 leak I = 1.4 uA, near S2 leak I = 3.3 uA.
We unbiased the detectors, switched off the NIM, CAMAC, and RAL crates, and also switched off the preamp power. We didn't wanted anything damaged from potential overnight thunderstorms.
At 20:35 the pressures read (in mBar):
- TPU1 = 6.3e-6
- TPU2 = 8.0e-7
- TPD1 = 1.2e-6
- TPD2 = 1.2e-6
- CHUP = 6.2e-6
- CHDW = 1.4e-5
|