York W detector 2635-19

1037um

As you can see...

The thick carbon target, to be used for background runs for the thick CH2 measurement was supplied by Marek.

He measured it to be 120um thick (with a micrometer), and says it's low density carbon (1.03g/cm3).

The range of a 68 MeV Ne beam in this is 67um.

Range of 16 MeV alphas is 266.5 um.

 In attachment are the peak position in the photodiodes (with high gain setting) for the target thickness measurements.

I've analysed data from runs 4 to 12, which were the alpha irradiations of PD1 and PD3 through the foils.
Time, 'target', which PD is being irradiated.

21:02 Ch2A 1
21:30 Ch2B 1
21:49 Ch2C 1
22:09 Ch2D 1
22:30 AuC 1
23:16 2mm 1
23:35 Au         3
24:23 4mm 3

Data are being sorted with sort.f, with the new variables file which has offsets and gains. 
The offsets should be fine, but the gains are based on data taken with the PDs in their
low-gain 'run' configuration. For these data, to be able to resolve energy loss at the scale of 10's keV, 
we needed higher dispersion, so the gains were increased. Hence the gains in the variables file 
cannot be used. We do a new energy calibration here.


Peakfind has been used to find the centroids of all relevant peaks. 
Using 2mm hole data (no energy loss except for deadlayer) I find the calibration of PD1 to be 4.74379 keV/channel. 
Likewise, using 4mm hole data for PD3 I find PD3's energy calibration to be 4.78963 keV/channel.


Energy losses for the three alpha peaks (5155, 5485, 5805 keV) are then:

Foil ch2-A: 

1077.0 keV
1020.4 keV
972.9 keV


Foil ch2-B

1121.6 keV
1060.8 keV
1010.9 keV


Foil ch2-C

1059.6 keV
1005.1 keV
952.2 keV


Foil ch2-D

1162.3 keV
1101.2 keV
1072.6   keV


Foil thin ch2+flash gold

12.3 keV
8.5 keV
10.3 keV


Foil: Thick gold

50.7 keV
50.4 keV
52.4 keV

 Wednesday morning:

4 new windows were tested last night. 2 very good.

Now venting to install and test Faraday cup, install and test camera.

Remaining to do list:

Before beam - 

 beamline on SEBT back in and pumping upstream section

(measure C and C/Au target thicknesses if time)

replace 4mm collimator on plate with 10 mm for tuning

confirm PD0 problem just connector

install detector shields and pump down

walk round TUDA and check no grounding compromises

Before running -

runplan

procedures tick list for H2

runlog and detector current list

exclusion zone and Al plate before running H2

Handover from last shift was...

1. Running at 4.11 MeV/u at about 15enA (5+)

2. Would like to take more beam but already at situation where deadtime about 50%.  They have been raising thresholds on the inner strips of S2-1 to try and cure that, but it doesn't appear to have helped.

3. There is a sort of the past runs ongoing to use the counts in spectrum 4200 (coincidences) to estimate when there is enough data at this energy to move to the next.

Analysis:

Firstly, the locus being looked at in the S2-1 vs S2-2 to make this judgement cant be right.  There are already thousands of counts in this in a replay of a one hour run  Jamie's estimates in the run proposal were for 1,000 in 12 hours at 10**8/s.  We are currently at 20% of that beam intensity and the deadlime is about 50%, so should be seeing 10 counts in one hour.  The data must be somewhere else in the plot.  My guess is that the intense locus is elastic/inelastic scattering coincidences.  If this is the case then it maybe we have an issue in that these may be what is dominating the rate and it will not be possible to get rid of them from the trigger.

Looking at the S2-1 energy spectra, it looks like the raised threshold is cutting into potential data (maybe Alex who knows from the MC what energy the data extends down to should look at this and check).  The high trigger ratemust be from another channel.

Actions for this shift

1. With two people on shift and a requirement that we need two down in the area at all times, I don't think chasing thresholds is viable.  This will have to be left to the day shift.

2. Should continue the sorts so that we have the spectra available to make rate estimates once we know what we are looking for.

3. Should look at the sort code to see what calibrations are being used and so determine where on the coincidence spectrum the data should lie.

Plan for shift was to increase trigger thresholds on S2-1 and S2-2 to cut out the low energy "stuff" which is dominating our trigger rate, and preventing us from increasing the beam current. S2-1 thresholds were at 10mV and S2-2 at 25 and 30mV.

Increased all S2-2 thresholds to 30mV and took runs with S2-1  at 11, 15, 20 and 40mV. Trigger rates seem unaffected. Low energy peak in S2-1 spectra are unaffected, however the bump at chn. ~380 was shifted up as threshold increased.

Looking at energy-energy spectra from sorted data, see lots of events at very low energy (y axis), across all channels (x-axis).

Concluded that the low energy peak is real coincidence, so can't be removed by increasing trigger threshold (as it is in coincidence with stuff in S2-2), and the "bump" is singles, so is being cut out as thresholds are increased.

Not clear whether the low energy peak is reactions, or something else, but the result is we can't increase the thresholds to cut the rate and allow the beam current to increase.

Following discussions with Brian, the interpretation of this may not be correct.

Things have been running smoothly from 4 pm to midnight.

Reading in FC0 = 120-130 epA

Total trigger (accepted trigger) = 7500 (4000) Hz

Gas temperature has dropped from 30 to 22 deg C (due to evening cooling of experimental hall?). As a consequence, pressure has dropped by 0.2% (current value 249.8 torr).

Runs during this shift: 87, 88, 89, 90, and 91 (still running).

Runs 87-90 have been analyzed with sorting code.

Good night

At approximately 7pm, noted that trigger rate in S2-1 had dropped by factor of ~20. Detector had tripped off due to leakage current reaching 8uA - spotting this was delayed as camera (or web-browser) monitoring currents had frozen. Current trip point has been increased to 12uA, and the beam intensity lowered to try to preserve the detector through out the night.

At some point this may be increased again but that will have to await a discussion of how much the detector can take. Replacing it would take ~6hrs so ideally we'd like it to survive until the end of the experiment.

For the time being we need to monitor the leakage closely (and ensure the web cam image is updating) and if the trip point is approached, either lower the beam current or switch off the detector for a while to allow it to recover, or both.

still running at 3.98 MeV/u

19:08

S2-1 had tripped off due to leakge current going above 8uA

Camera watching leakages had also frozen so didn't realize until we checked downstairs

asked to lower beam intensity down to 55epA (was 120epA) @ run119

23:22

asked to set beam intensity to 100epA

upper limit of leakage set to 20uA

S2-1 leakage current ~9.93uA

Sorted Runs:

run120

run121 still running

Please note that these procedures are not perfect and other small operations not listed may need to be carried out. Some mistakes may still exist in these procedures which could introduce significant risk if not spotted and corrected during the process. These should only be carried out by people confident they understand the system and the purpose of each step, giving due consideration to each step to ensure it is appropriate and safe.

In other words, don't blame me if it all goes horribly wrong!

S1287 data files R1_*.gz to R100_*.gz transferred from directory
tuda2:/data2/data/S1287 to directory tuda3:/data3/data/S1287

This releases c.18Gb of space in the tuda2:/data2 filesystem

1) PD run with gas (250Torr) - done

2) Pump down to 50 Torr - done

3) PD run - done

4) Take data (PD out) at 50Torr ~2 hrs. ~110epA - done

5) Pump out - done

6) PD run (no gas) - done

   a) remove 5mm collimator and run without gas, ~100epA (no PD) - done

7) Complete H2 venting process - done

8) Open up, sources in (window off) - done

9) Pump down - done

10) alpha data (some of the S2-1 inner strips look  very ill indeed , but all but one or two show clear triple-alpha peaks.  - done

11) pulser walkthrough - done

12) vent and open up - done

13) dismount detectors and re-entrant flange - done

14) pub!

Done - finished at 7.30pm, pitcher of ale methinks. 

Attached is a spreadsheet summarizing all the run information from the experiment.

Attached. Book 13 is split into 4 sections as otherwise the file is too big for the elog to accept.