The ESR team is changing the beam energy to 6 MeV/u.

Si HV and current was switched in the last documentation.

Beam stacking. 3 pulses, stochastically cooled and stacked on an inner orbit

measured beam lifetime after the second deceleration using parallel plate Schottky detector and the RSA5103 spectrum analyser. Analysis code can be found here:

https://github.com/xaratustrah/e127_scripts/

The plots here were produced using the script:

https://nbviewer.ipython.org/github/xaratustrah/e127_scripts/blob/main/lifetime_calculator.ipynb


UPDATE 2022-06-30:

Life times have been slightly corrected. Please see attachment.


Filename	Start Frame	Correct Lifetime [s]	Mean [s]
pgamma_lifetime-2021.05.25.21.56.37.593_on.tiq	29500	1.43	
pgamma_lifetime-2021.05.25.22.02.16.618_on.tiq	29500	1.55	1.49
pgamma_lifetime-2021.05.25.22.07.22.369_off.tiq	53500	1.75	
pgamma_lifetime-2021.05.25.22.13.24.787_off.tiq	34900	1.89	1.82

Beam is back; It is now being optimized

Recoil detector files backup to lxg1260:/data.local2/hillenbrand/Laszlo

General remarks to the MOCADI simulations:

1. scraper size vertically > (p,g) spot at the scraping position --> (p,g) can be separated by truncating the backscattered Rutherford events in the energy.


2. replacing the atomic masses to nuclear masses does not change significantly the absolute positions of the (p,g) and the Rutherford. However, the (p,g) spot in the simulation seems bigger using the nuclear masses, than in the 124Xe experiment with a factor ~1.6.


3. going for lighter elements, the separation between (p,g) and Rutherford getting better, than slit can be placed even more far from the beam in x (radial) direction. For 124Xe the minimal distance from the beam axis is <4cm, for 73As it is <7.5cm.


4. in the simulations the scraping is mostly until x=-inf. However, if the scraping is incomplete in x, we can end up with underlying background events below the p,g peak (see the last slides)! The Rutherford cone gets bigger by going down with A,Z. For 91Nb the minimal width of the scraper: x>6cm, for 73As x>7cm. Therefore, I suggest to have a scraper width x=9cm. For the y, y=6cm should be safe.


5. for lighter elements, the (p,g) spot size increases: in the simulation for 73As it reaches the detector size. However, the (p,g) spot size might be overestimated, please read the 2. point.

BaF2 detectors are deactivated nor for the following runs.

with these HV values the 6 channels are roughly gain matched, such that the 7.83 MeV Po-decay is around channel 5000.

I introduced a downscaling by a factor of 2^5=32 for the BaF2 during target OFF.
The reason is, that we get a lot reasonable x-ray counts (K-alpha, K-REC) outside target ON phase.
So i want to minimize our deadtime during target OFF, to be able to use the data efficiently if needed.
BaF2 is not really needed in target OFF.

On 30. and 31.03.2021 we did some testing with the 6 BaF detectors.

Trigger & threshold:
With a threshold at ~250 keV, each detector has an trigger rate of about 0.5kHz due to internal activity.

Energy spectra
All detectors showed the Na22 lines (511 + 1275 keV) and also the lines from internal activity.
The energy resolution was on the order of 8.5 - 11 keV, depending on the detector.

Time spectra
Raw TDC spectra showed self-stop peak.
TDC diff spectra (between detectors) show one main (sharp) correlation peak about 8ns = 30ch*0.293ns/ch off the zero. 
At very low intensity a time structure around this peak is visible in a region of 120ns around the main peak. This is not understood, the energy spectra look similar for all these time regions (above/on/below the main peak).
Additionally, the coincidence E-specta between detector 1 and 2 (gating on the main time peak), nicely showed only the 511 keV line from Na22 and some gras.

Overnight test run:
Det. 1, 2, 3, 4 with the Na22 source

lxg1275:/data.local3/e127/lmd_2021/test/
e127b_run0021.lmd
e127b_run0022.lmd
e127b_run0023.lmd
e127b_run0024.lmd
e127b_run0025.lmd
e127b_run0026.lmd
e127b_run0027.lmd
e127b_run0028.lmd
e127b_run0029.lmd
e127b_run0030.lmd
e127b_run0031.lmd
e127b_run0032.lmd
e127b_run0033.lmd
e127b_run0034.lmd

Gain matched HV settings: https://elog.gsi.de/esr/E127/289

Issues to solve:
- 2 missing HV channels
- Go4 Analysis not stable
- trigger not on Baf but on Si

All shifts until Monday morning (24th May) have been cancelled. 
Next update on further situation (in particular concerning the morning shift on Monday) will be given tonight .

I made a backup for the MCP data on my own GSI laptop. Looking for better solution...
the original "fresh" files stored at litv-exp@lxg1299:/data.local2/hillenbrand/Laszlo/

30angle:  E[keV] = 0.015898 *ch-1.91
90angle:  E[keV] = 0.0211075*ch-2.39
145angle: E[keV] = 0.01663  *ch-1.758