Checking SRIM 3.5 MeV 7Li is stopped in 9.06um mylar or 10.09 um CH2.

After the long run at 3.0MeV on 22/02/2018 we decided to put the 12um mylar back in front of the S2 and start tuning the beam for 3.45MeV 7Li. We also decided to tune the beam to a higher current of ~ 100pA to try and improve the detection rates.

At 20:54 The turbos were switched off. The manual gate valve for Ecodry 2, automatic gate valve for Ecodry 1, and line valves were closed.

Whilst the turbos spun down we removed the S2 preamp box from the top of the chamber.

At 21:31 the vent valve at FC-O was opened. At 21:49 we noticed the chamber was vented.

The S2 was removed from the chamber and 12um mylar mounted in front of it. The S2 was remounted in the downstream section of the chamber.

At 22:03 the manual gate valve was cracked open -> we began roughing the chamber with Ecodry 2. At 22:18 the manual gate valve was fully opened and we then opened the T1600 Backing valve allowing Ecodry 1 to pump the chamber. We then started the turbos.

During pump down the S2 preamp box was remounted on top of the downstream chamber lid. The lid to the preamp box was also mounted. The following pin diode preamp cables were reconnected: -15V, +15V, +ve test, input from lemo feedthrough, and HV.

By 22:34 the pressures in the chamber were CHUP = 1.3e-5mBar, and CHDW = 3.2e-5mBar. The S2 was biased to -130.3V, leak I = 1.54uA. The diode was biased to -70.1V, leak I = 0.00uA. The preamp power was switched on, correct currents were being drawn.

The target ladder was set to position 2, 80.024mm, no target or frame.

After tuning with no target, the GSSI slits were fully open at:

Up = 0mm

Down = 5.5mm

Right = 1.5mm

Left = 5.5mm

We found the following currents:

FC-4 = 740pA (upstream from bending magnet)

FC-0 = 430 pA (upstream from chamber)

FC-E1 = 70pA (downstream from chamber and GSSI magnet)

The target ladder was moved to position I, 95.010mm, blank 3mm frame.

After further beam tuning we obtain currents:

FC-E0 = 330pA

FCE1 ~ 200pA

Transmission: ~63%

At 23:33 CHUP = 6.5e-6mBar, and CHDW = 1.7e-5mBar. S2 bias = -130.3V and leak I = 1.66uA. Diode bias = -70.1V and leak I = 0.00uA.

We decided to call it a day. Both the S2 and diode was switched off for the night. The accelerator beam voltage ~ 1.4730MV.

Raffaele let a note for Liz to improve the transmission to 70% the next morning (23rd).

See next eLog entry #19 to continue the beam tuning adventure.