Emittance Measurement with Optical transition Radiation (OTR)

Papers

File:M.Castellan NIM A357 1995 pp231.pdf

Set Up

Determining if we are getting OTR

To determined if what we are seeing is OTR, we need to see a cone. OTR is polarized. If use a polarizer we can determined the cone we are seeing is polarized. Then we can be sure that we got OTR.

The distance from the center of the OTR target (also the center of the 6-way cross) to the closest position we place our first lenses is 13 cm.

Edge to edge OTR cone diameter size ([math]4\theta[/math] angle,[math]\theta=\frac{1}{\gamma} = \frac{1}{\frac{10}{0.511}}[/math] ) at this distance is 2.665 cm.

We need to put lenses or achromat to focus on infinity to see a cone. We had an lens telescope that can focus on infinity with diameter of 2.6 cm. We might be able to push this telescope to a distance closer that 13 mm. We might be able to push telescope to 12 cm distance, then we cone will have diameter of 2,46 cm. Then we can see all the cone. We should do an experiment on this next time.

Beam Line Alignment

From the March 3rd Run, we can see that the beam line is not aligned. We need to align it.

Equipments Needed

1) Laser beam. 2) Lase beam Stand. 3) Mirrors. 4) Crosses.

Beam Based Alignment Procedure

Find Best Steering Set

1) The most upstream solenoid is used to adjust the gun emmittance and the downstream solenoid will adjust the beam size. Turn off both solenoids

2) Turn off all the quads.

3) Maximize the transmission along the zero beam line using the front and rear steering coils

4) Turn on the beam downstream solenoid and to adjust the beam spot size. If the beam spot moves on the OTR target, then the beam is not coming out of the HRRL.beam center moves on the screen?

5) Adjust the HRRL steering coils until the beam spot does not move when the downstream solenoid current changes.

6) Repeat step 3 and 4, until beam center does not change by change solenoid strength.

This is the best steering set. Record corresponding current settings.

Quad centering

1) Turn on just one quad at a time. Change quad strength, see if there is steering by the quad.

2) If there is steering by the quad, move the quad. If the steering is vertical (horizontally) move the quad vertically (horizontally). Do it Until beam can not be steered by the quad.

3) Repeat 2 for all the quads.