Explore polarization transmission efficiency with near integer working point

June 10, 2009

Mei, Don, Angelika, Wolfram, Haixin, Yun, Al, Greg, Michiko, Kevin, RobFulvia, Vadim, Guillaume, Thomas, Todd, Vincent, Carl, Steve, Anatoli

• Goal: – Look for new working points which 100% polarization can be achieved– Candidate:

• Near integer: > 0.94• RHIC pp design working point: 0.81

• Setup: pp94nearInt– Blue wp: Qx=27.88, Qy=0.955– Yellow wp: Qx=27.82, Qy=28.81

Motivation

2

3/47/10

11/1

6

old

wor

king

poi

nt

curr

ent

wor

king

poi

nt

Py

15/1

6=0.

9375

13/1

411

/12

9/10

7/8

5/6

11/1

4

• Build pp94nearInt:– Steve, Al, Don

• Ps preparation: Don, Carl, Chaofeng, …– Exam pp94nearInt ramp with no beam: 2 3-hours APEX sessions

• Failed ps• QPA problem• Blue ups problem

• Switch mains coefficients: Carl• Prepare BBQ and tune/coupling feedback

– Michiko, Al, Yun, Kevin, …

• Finalize pp94nearInt– Guillaume, Vincent, Steve

Preparation

• Lowered Qy to below 0.9 to establish circulating beam• Set Blue Qy to ~0.94 to establish good lifetime at injection.

Orbit correction in Blue with near integer tune was excised. Good orbit was established.

• Spent ~ 3 hours at injection to setup tune feedback in Blue for near integer tune. Al hardwired the coupling correction to zero in his code to force coupling feedback off as Yun suggested

• Yun measured coupling angle in Yellow at injection• Both beams reached top energy after two ramps which

pushed beam to one stone per ramp. Orbit distortion along the ramp ~7-8mm rms. Orbit at store was corrected.

• Spent 3 ramps to do orbit correction along the ramp. Permit was pulled for all the ramps due to instability right before store stone. No polarization measured.

What have been achieved?

Summary of ramps

Summary of ramps

Ramp ID Blue eff. Yellow eff. note

10892 0 0 Beam died at t8 due to bad orbit

10893 0 0 Died at snapback

10894 67.4 19.4 Blue: ~ 7mm vertical orbit rms.Yellow: instability at snapback

10895 96.6 27.5 Blue died right before store due to over voltage of bi8-tv2Yellow: instability after snapback

10896 Permit pulled right before store stone due to blue instability

10897 0 0 Permit pull due to Blue loss from instability right before store

10898 0 0 Permit pull due to Blue loss from instability right before store

First ramp both beams up to 250 GeV

Yellow loss due to instaility

Blue Beam, Orbit and Tune

Yellow Beam, Orbit and Tune

• Another 8-12 hour session– Correct chromaticity and make beam survive to store stone– Improve orbit correction as well as beam transmission efficiency– Measure polarization– measure polarization as function of Qy from 0.935 to as high as

possible. This may require couple of iterations of optimizing ramp to correct orbit

– Increase # of bunches to > 28 bunches per ring– measure polarization along the ramp if time allows

Plans