2023-03-22

Machine Status

Vacuum is 2.4e-7 Pa (yesterday was 2.4e-7 Pa).

Linac is a bit slow to start up today, and beam commissioning is taking longer than the other days. Machine is ready at 12:00.

TORA signal is greater than around, ±300 mV at injection. This is a huge increase in the beam current due to RFQ optimisations. 

FAB signal is much larger in bunched region.

Equipment

Scope settings have been verified. 50 Ω termination on CH1, 500 MSa/s, 50 ms window.

Measurements

Today's experiment will primarily be an energy-gap sweep with coasting time; if there is adequate time, then we will repeat these energy-gaps without coasting time. Shinji has provided AWG scripts for several energy gaps, and we will complete these in order of acceleration time; with beam-2 starting lower energy than beam-1 and ending with a higher energy.

Today we will position Beam 2 above and below Beam 1, so we need to assign a sign to the energy gap. In order to be consistent with the earlier description of energy gap, we have chosen the convention that the "Energy Gap" is ((Beam-1 energy) - (Beam-2 energy)). When beam-2 is a lower energy than beam-1, the gap is positive.

We will take measurements with delay 25 ms, 122 ms, 273 ms and 360 ms. The approximate arrangement of the scope windows is shown below in relation to the RF voltages. 

Measurements didn't start until around 12:00 due to problems with the linac.

Measurement 1 - Case 1 - One Beam

Schottky signal is very clear due to the increase in beam current. Harmonics 10 and 11 are visible; although 11 is small. Momentum spread is measured by eye at harmonic 8 and is full size 2.46e-3.

Measurement 2 - 6.960 ms (+235.4 keV gap)

By eye at harmonic 8, dP/P = 5.74e-3

Measurement 3 - 6.970 ms (+200.6 keV gap)

By eye at harmonic 8, dP/P = 5.25e-3

Measurement 4 - 6.975 ms (+182.5 keV gap)

After lunch, AWG crashed and recommissioned was done to adjust trigger parameters. Beam condition at Tora: ±200 mV at flattop (fluctuation can be seen to ±150 mV). Start data taking at 15:00. By eye at harmonic 8, dP/P = 4.79e-3. 

15:30: Linac down.

16:30: Machine is still not operational

16:51: Machine is operational again. We will move to 7.01 ms to observe beam-2 above beam-1.

Measurement 5 - 7.010 ms (+45.5 keV gap)

16:55: Linac is down again.