We recognized that the output power of the pump laser was instable when externally triggered with 200kHz (stand-bye frequency of ESR). Therefore, we changed the coarse timing offset of the pockels cell trigger compared to the flash lamp pulse from 215µs to 219.9µs. 
Thereby, the output power increased from ~600mJ to 620mJ, and the PTP stability improved from 15% to 10%. The RMS stability improved from 2% to 1.2 %. With these settings we had UV pulse energies of 20mJ.

In the SetParameters.C file is a parameter called fPar->piPhaseOffset. It was shifted from 100 to 50 in order to see ion bunches in the pmt signal and laser pulses in the photodiode signal during the same revolution in the TDC spectrum. Note that this parameter must be taken 
into account when setting the window conditions of the arrival time in the SetConditions.C file. 

• right side: the thorium beam.
  
• left side: a satellite peak (isobar).
  

We have switched off all 3 PMTs  !

current settings of PMT voltages and thresholds at the CAEN CFD:

PMT South   [HV ch2: 2700V]  [CFD ch0: 8]

PMT Middle  [HV ch1: 2850V]  [CFD ch1: 8]

PMT Nord    [HV ch3: 2850V]  [CFD ch2: 9]

We tested the PMTs again, this time with an UV LED that is mounted at a window close to the XUV detector.
PMT south showed a very clear increase in count rate from about 1 to 50 Hz.
PMT mid also showed a small increase by a few Hz.
For PMT north there was no great change between LED off and on, but we think that the count rate also very slightly increased. Note, that PMT north is also the furthest away from the LED.

Also we saw a difference between single- and multi-photon events at PMT south.

Carsten and Kristian changed (18:00) the thresholds of PMT north and PMT middle in the ESR cave. 
See picture below. The effect is negligible. 


Carsten will now (18:05) change the channel of the pre-amp of PMT north. 

We have made two foam rings (outer diameter ca. 70 mm with a thickness of 10 mm each and placed them successively underneath PMT north. 

ring 1: ID = 55 mm 
ring 2: ID = 47 mm 

Without rings we had measured ca. 20 counts per channel in a time of about 7 minutes. (1st picture below) 

With ring 1 we have measured ca. 18 counts per channel in 7 mins. 

with ring 1 and ring 2 we have measured ca. 15 counts per channel in 7 mins. (2nd picture below)

It is clear that the rate of PMT north decreases with increasing distance from the beampipe. 

At this point it is not yet clear to us if the experiment will benefit from the 2 rings. 

If the rings should be implemented, we propose to have one proper ring (20 mm high) made by the mechanical workshop. 

We noted that the dark countrate of PMT north is about 20x higher than that of PMT middle. 

We went into the ESR cave to look for stray light. 
We decided to put a black cloth over all the PMTs. 
Also we made the tubes of the N2 airflow to the PMTs black (tape around). 
This did not make a significant change. 

We exchanged PMT north (same type 9423B) to see if that made a difference. 
It did not really change either. 

PMT north = 2650 V 
PMT middle = 2700 V 

The first picture below shows the dark rates for these two voltages. 

At about 17:00 we changed the voltage of PMT north to 2700 V. 
This did not change anything. 


Carsten swapped the cables of PMT north and PMt middle (inside ESR, before the amps) at 17:14.
The second picture below shows the result of that. 
Now black and red are exchanged. 


Carsten swapped the cables back again (17:20). 
Carsten and Kristian will look at the PMT signals in the ESR cave. 

For PID with rionid we used: 
- LISE file from last year (attached.
- .npz file from 410 RSA (attached).

15:45 Right now, we are waiting for stable conditions again. There are problems with both the ion source and the accumulation in SIS.

16:20 SIS and source look better now, but now ESR makes trouble. The stacking looks off and after deceleration and cooling barely any Th-ions are stored. The positions of the scrapers seem to be wrong. Carsten is trying to fix it.