Beam Monitor

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Beam Monitor Current Status:

The two beam monitors with a segmented frame design using guard rings to drain off leakage current are currently installed. The monitors are labeled M1 and M2 and have the following fill gas compositions:

Fill Gas M1 M2
He3 (torr) 14.8 10
N2 (torr) 736.8 766.9


Beam Monitor Voltage Scan

To test recombination in the beam monitors a bias voltage scan was performed with the M1 and M2 beam monitors. A variable high voltage power supply was used, and the voltage from the power supply was verified using a 10:1 voltage divider and a multimeter.

File:M1VoltageScan-0V-2000V.jpg

Voltage Scan of M1 Monitor. Divided by M2 monitor held at constant voltage to control for beam fluctuations.

File:M2VoltageScan-0V-2000V.jpg

Voltage Scan of M2 Monitor. Divided by M1 monitor held at constant voltage to control for beam fluctuations.

These voltage scans were done at approximately 650 kW beam power.


Here is an update on the beam monitor:

The second chamber for the monitor was manufactured by Atlas technologies and was delivered in March (03/15/2008).

After successful testing of the first generation monitor at LANL (twice, in 2009, separated by 6 months), we had trouble seeing any signal at the Oak Ridge test beam. In addition we found that a large leakage current of 30 nA had developed. As a consequence a new frame was designed, which separates the signal and the HV frames (the old frame was monolithic ) and uses guard rings connected to ground. The chamber was operated at up to 1.7 kV, without sparking. The current was measured to be 0.08 nA at 1.7 kV.


Below are several pictures:

1. New frames:

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2. New frame assembly

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2. Open monitor

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3. Measurement Setup

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4. Measurement (at 1.7 kV with air inside chamber)

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Previous update:

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The chamber for the monitor was manufactured by Atlas technologies and was delivered this past week (09/30/2008).

The above figures show the chamber, the wire frame and various other parts.

On Friday (10/03/2008) we took the wire frame pieces to the nano fabrication lab at the U of Manitoba and to deposit the conducting traces on the wire frame, using sputtering (pictures below). We deposited 200 microns each of chrome, followed by copper. The resistance along the traces from one end of the frame to the other is 80 Ohms

Next week we will begin to string the wires, after which we will attach the frame to the housing.

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