Improvements HRRL Positron Runs July 2012

1. Make T2 holder without vertical 45 deg angle.

2. Improve TDC inputs, and DAQ system (use veto on the CFD).

3. Put better (more sensitive, thicker) scintillator at the exit of 90 deg, so I can measure the numbers of positrons.

4. Take more data on 3 MeV and 4 MeV positrons.

5. Measure the energy spread of positrons by changing slit width for different energies (1, 2, 3, 4, MeV).

6. It seems we don't need the ion pump at 90 deg beamline, it can be removed next time.

7.

Run Plan

Tune electron beam

Tune Energy

1. Put the RF power knob desired energy region.

2. Tune RF first, then solenoids to get some current on the 0 deg Faraday cup.

3. Bend the beam 45 to scan the energy using Faraday cup at 45 deg exit.

4. Tune the RF power knob and repeat above steps to get the desired energy.

Tune to maximize current

1. Tune RF first, then Solenoids to get some current on the Faraday cups.

2. Use gun steerers to maximize the current on the FC.

3. Use output steerers to maximize the current on the FC.

4. Use quads to maximize current on the Faraday cup.

5. If the energy of the beam is higher than 12 MeV, electron beam can be observed. Beam size can be minimized by using OTR screen.

Bending the beam 90 deg

1. Turn on Dipoles, set them to turn same energy.

2. Bend the beam, beam can be observed by Faraday cup. The current is small. Energy scan and currents transmission measurements can be done.

Calibrate beam current monitor

1. Set the current at the scintillator to 500 V (this is for Dr. Dale's scintillator, for others scintillaotr start from lower voltage).

2. Set the current of the accelerator for full current.

3. Decrease the current of the accelerator by steps. For example:0.8, 0.6, 0.4, 0.2, 0.1 of the full current.

Measure electron momentum distribution

Momentum of the electron beam can be done by bending the electron beam by dipole 1 (D1), and observe the bent beam at the 45 deg Faraday cup (FC45).

1. Bend the beam using D1, turn off D2.

2. Observe the beam at FC45.

3. Start from lower coil current on D1, increase by steps. The current on the FC45 should increase first, then decrease. Save the scope images with the area of the current measured.

Measure Positron Momentum distribution

Positrons generated from T1 are too low to be observed Faraday cup. Scintillator need to be used to boserve positrons.

1. Optimize the magnet settings for electron mode

1. Optimize electron beam, then put T1 in.

2. Set scintilator to low voltage region around 500~600 V.

3. Set magnets to electron mode. observe electron signal on the scintillator. Optimize magnet for maximum current.

2. Optimize the magnet settings for electron mode

1. Switch the polarity of magnets after T1 to positron mode.

2. Optimize the magnets for positrons with different energies. (Positrons and electrons after T1 has different energy distribution, magnets need to be optimized for positrons.) Positrons incident on the scintilator can be observed, and be used to optimize magnets.

Positron rate measurements

Target in , Target out, Sweep magnet