----
The frequency of the primary beam 238U82+ at the injection:
Ucool = -360 V
Frev = 1.974647 MHz without bump
Frev=1.97387 MHz with bump
---
ID:
246 MHz + kHz (+/- intensity) ID
521 +++ 238/92+
565 +.    230/89+
595 +++ 235/91+
642 +.    227/88+
670 +.    232/90+ 
693 +++ 237/92+ (strongest line)
721 +.      224/87+
744 ++.   229/89+ (our Th line)
767 ++.   234/91+
822 +.     226/88+
845 +.     231/90+
867 +.     236/92+
901 -       223/87+
922 +.     228/89+
942 +.     233/91+
1001 +.    225/88+    
1020 ++.  230/90+
1039 +.    235/92+ 
1100 +.     227/89+
1211 + <- far off

Setup at ESR is carried on - stopped the long-time NTCAP run from overnight,

Lifetime still is short

From experience, the lifetime of the beam in the storage ring should be on the order of magnitude of hours, however, we observer beam lifetimes of the order of 10ish minutes. This suggests either a beam loss mechanism, a totally wrong species or a combination of both.

Yesterday (Elog entry 46) it was verified that the main beam is indeed 229-Thorium in the ESR.

2024-06-13: After discussion (phone) with Markus the lifetimes are reasonable and are dominated by recombination in the cooler.

To realize the shortest bunches possible, we check the bunch length as a function of two different bunching amplitudes. With the bucket fill set to 1.0 we observe the spectra compiled in attachment 1. The second attachment is recorded with a bucket fill 0f 0.2.

For an RF amplitude of 0.2 we do not observe bunches any more but a coasting beam. In the shottky spectrum we can resolve a shift of the signal and thereby adjust the electron cooler voltage to the bunching frequency to within 1 V.

U_e-cooler = -104410 V
I_e-cooler = 80 mA

Estimate of storage lifetime using my code 'hydrocal':

 ion mass in u ...................................: 229
 ion nuclear charge ..............................: 90
 ion charge state ................................: 89
 beam energy in MeV ..............................: 45501.1
 beam energy in MeV/u ............................: 198.695
 beam beta .......................................: 0.566309
 beam rigidity in T m.............................: 5.4944
 ring circumference in m .........................: 108.36
 ring acceptance in mrad .........................: 2
 ring temperature in °C ..........................: 25
 ring vacuum pressure in mbar ....................: 3e-11
 residual gas density in m^-3 ....................: 7.28767e+11
 residual gas composition 
  Z   %
  1  93.43
  6   2.23
  7   0.75
  8   3.29
 18    0.3
 cooler length in m ..............................: 2.5
 electron current in A ...........................: 0.2
 magnetic expansion factor .......................: 1
 electron-beam diameter in mm ....................: 50.8
 electron density in cm^-3 .......................: 3.62844e+06
 cooler cathode temperature in meV ...............: 110
 cooling energy in eV ............................: 109000
 space_charge (0th iteration) in eV ..............: 44.3477
 space_charge (1st iteration) in eV ..............: 44.341
 transverse temperature in meV ...................: 110
 longitudinal temperature in meV .................: 0.2
 RR nmin .........................................: 1
 RR lmin .........................................: 0
 RR nele [no. electrons in subshell (nmin,lmin)] .: 1
 RR nmax .........................................: 128
 RR enhancement factor ...........................: 2.5
 RR alpha in cm^3 s^-1 ...........................: 8.04602e-08

 beam lifetime due to multiple scattering in s ...: 1.86e+06
 beam lifetime due to single scattering in s .....: 7.51886e+07
 beam lifetime due to charge capture in s ........: 3.5516e+06
 beam lifetime due to stripping in s .............: 1e+99
 beam lifetime due to recombination in cooler in s: 148.466
 beam lifetime with electron cooling in s ........: 148.46
 beam lifetime without electron cooling in s .....: 1.20121e+06

 detector count rates for 1E6 stored ions and a residual gas pressure of 3e-11 mbar: 

       recombination detector from ecool (Hz) ....: 4575.41
     recombination detector from res.gas (Hz) ....: 0.0545666
    total rate on recombination detector (Hz) ....: 4575.46

        ionization detector from res.gas (Hz) ....: 1.93798e-94

It seems to be that there are some problems with the injections in the ESR.
The last 2 accumulation cycles showed that wheter only a small amount of ions are injected into the ESR or the injection is missing.

Photos of the last 2 accumulation cycles are attached.

We ask if there are some problems with the ESR or with the SIS18, because the particle number in the SIS18 is also decreasing... 

Cooling Time in SC7 increased from 9s to 12s

All quadrupole and dipole magnets at SIS and ESR are out of order. Repairs can be expected earliest tomorrow evening. No shifts will take place before 6pm. Have a look at your mails for details.