2023-01-17
09:50 Accelerator start procedures begin
Ishi-san says that revolution frequency at kicker needs to be c. 3.9MHz -- this corresponds to the 100MeV AWG script from Shinji. Flat top frequency of 80 and 90 MeV scripts is too low and is expected to miss the kicker.
Calculated parameters:
100MeV: Total energy: 1038272000.0eV Radius: 5.23495194439522m Frequency: 3902745.5428670556Hz
90MeV: Total energy: 1028272000.0eV Radius: 5.200855783046683m Frequency: 3753454.0361935464Hz
10:45 adjusting relative phases of 3 RF tanks (accounting for daily fluctuation in conditions and performance e.g. ion source behaviour)
~10:55 beam operational
11:00 Good sidebands observed from kicker operation at (c.107MeV) revolution frequency 3.95MhZ using normal KURNS RF programme. Sideband position at 3.21875Mhz. Sidebands disappear when kicker timing is changed so that it doesn't interfere with the beam (i.e. sidebands are confirmed due to kicker-induced oscillation)
Corresponding tune 0.185127
11:05 First test: 100MeV acceleration and activation of kicker at different amplitudes
RF amplifier overloaded
Reduced flat top time of RF programme from 4ms to 2ms
Reduced rep rate of machine to 20Hz (?)
AWG trigger offset initially set 2.156
Trial and error adjustmentup offset to increase the intensity on the bunch monitor, little change in intensity between 2.156 and 2.146 - offset set to 2.149
Tried adjusting the timingof the kicker such that the kicker tiggers at 26.560, the flat top starts at 20.2ms.
No side bands seen on the frequency analyser
11:45 Septum magnet excited: parasitic loss of main magnet flux can be caused by septum. In order to compensate the septum magnet is excited
Data taken from this run:
Choosing this sideband (blue line) gives Tune = 0.16049491662658774 (compare tune from KURNS normal AWG script sideband measurement earlier)
Seems reasonable compared to kurns tune diagram (1-calculated tune)
11:?? Second test: Try 107MeV flat top AWG script to see if that produces a side band. 107 MeV is the energy at which we saw a side band for the regular kurns AWG script.
Beam is lost for kicker voltage 40kV
Reduce kicker voltage but beam loss persists at 20kV
Adjust kicker timing
12:06 SME offset 26.509ms (original)
12:07 Kicker offset 28.150us SME offset 27.929ms
12:10 reducing kicker voltage to zero to see if beam loss persists (i.e. is the beam in the kicker) -- theorised that we may be hitting septum magnet
frequency 4.006MHz - this is too high.
"107MeV" from KURNS script earlier is based on measurement using detector -- not correspondence to accelerator modelling.
We calculate that in our model a 103.6MeV energy corresponds to the frequency of 3.95MHz. Regenerate AWG script with this target energy
12:27 new AWG script run, beam loss is gone
kicker offset 27.06 microseconds
SME offset 26.829ms
kicker strength 20kV
Data taken, no obvious sideband
12:50 lunch. Ishi-san says that the ion source is behaving strangely today (less arc current than usual). He will play with it over lunch. Reduced intensity may be removing sideband signal
after lunch plan:
Continue with 103MeV test
Repeat 100MeV test with new ion source calibration, aim for better data
kicker on
kicker off
20kV, 40kV
13:51 - try with a differnt kicker magnet to see if we can observe side bands
No side bands observed with the other kicker magnet, we will g back to using the original kicker magnet
14:16 Test with original kicker, 20kV
Data extracted but no side bands visible in spectrum.
14:24 Test with 100.9MeV script 2ms flat top
kicker timing initially 26.560 microseconds
Kicker voltage set to 20kV intially
sme 26.399
Kicker timing adjusted to 28.660microsec to ensure the kicker fires during the flattop
SME adjusted to 28.499ms
No obvious side bands oberved for 20kV
Using the same AWG script as above, changed kicker voltage to 40 kV
Observed the spectrum below
50kV experiment
Peak corresponds to fractional tune of 0.232, persists when window is changed. 1-0.232 is 0.868, close to the nominal KURNS fractional tune. This looks like evidence of a valid tune measurement, but not necessarily an amplitude dependent tune shift
15:13 begin run with normal KURNS RF script with 20 kV kicker voltage (nomimal Kurns RF script has no flat top)
normal opertion rf offset 1.491ms
normal operation sme offset 26.679 ms
nominal kicker offset 26.850 us
Sidebands not observed
Intensity of beam and therefore the amount of signal could still be limited by issues with the ion source
After changing ion source settings beam intensity increased.
Side bands observed before the kicker fires - lower side band at 3.553MHz, main frequency at 3.821MHz (fractional tune ~0.0678
similar phenomenon to peaks at 0.07 in earlier measurements?
Nothing after kicker activation
Kicker moved 10mm inwards
Now seeing clearer side bands which give a realistic tune.
Kicker voltage 40 kV: tune 0.1937
Kicker voltage 55 kV: tune 0.1917
'double peak' due to proximity to coupling resonance?
vertical position data shown below. highlighted peak gives a tune of 0.2258
Kicker voltage 10kV: tune 0.189060
Kicker voltage 0