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

Steering the beam out of cavity straightly

1) Dis-attach 2 solenoids connected in serial.

2) Turn off all the quads.

3) Play with steering coils on the back and front of the cavity to get maximum transmission to the FC.

4) Change solenoid strength, see if the beam center moves on the screen?

5) If moves, change steering coils to compensate.

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

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.