Status of Crystal Measurements at the Tevatron

1. Status of Crystal Measurements at the TevatronDean StillDecember 6, 2007Fermilab Crystal Collimation Workshop

2. Status of Crystal Measurements at the Tevatron • Overview of Beam Studies for 2007 • Tevatron Crystal Collimator System • History of Beam Studies for 2007 • Summary

3. (Analysis by V. Shiltsev) Overview of 2007 Beam Studies Tevatron Crystal channeling at 980Gev Motivation for Beam Studies for 2007: • Results from Tevatron beam studies in 2005. • Demonstrated channeling at 980Gev. • Demonstrated that proton halo loss at CDF IP could be reduced by factor of 2 as predicted. Demonstration of Halo Reduction By factor of 2

4. Overview of 2007 Beam Studies (2) • Results CERN RD22 experiment (Sept 2006) Demonstration of volume reflection are also key factors for defining 2007 goals. • Based on the possible application in the LHC for Phase II collimation. (Cern RD22 – Volume Reflection)

5. Beam Direction 5mm Goal of 2007 Tevatron Beam Study: • Replace the “O” shaped crystal with a strip type crystal and repeat study in Tevatron. • Goal for 2007 Beam Study: • Use End of Store study to demonstrate difference in halo loss for strip crystal and tungsten target. • Demonstrate this difference for channeled and volume reflected (VR) beam. (Single Plane only) “O” Shaped crystal 440 urad bend angle Crystal Courtesy IHEP, Protvino Strip type crystal 1mm wide X 3mm long 150 urad bend angle (INFN, IHEP)

6. Tevatron Collimator Layout Install Crystal Collimator at E0 to replace a Tungsten Target and utilize the rest of the collimator 2 stage System. Proton Set 1 D49 Tar, E03 & F172 2nd Proton Set 2 D171Tar, D173 & A0 Pbar Set 1 F49 Tar, F48 & D172 Pbar Set 2 F173 Tar, F171 & E02

7. LE0PIN 23.731 m 33.115m LE033 BLM 23.731 m Channeled beam At E03H 3.5 mm crystal channeled beam Flying Wire Pin Diode E03H Collimator E0 Crystal Layout

8. Crystal Collimator System Protons PIN Diode BLM Laser angular instrument: Angular range = 4mrad. Tevatron style BLM downstream Of E03H collimator (T:LE033) E0 Crystal Collimator Assembly. Angular scan range = 8mrad E03 Secondary Collimator

9. History of the 2007 Beam Studies • From January 21 – February 19 conducted ~ 16 hours of end of store beam studies and concluded that crystal was mis-aligned by 14 mrad. (Realigned April 3, 2007) • On May 25 conducted the first scan after the realignment to find the channel.

10. T:LE0PIN T:LE033 4 urad scan 2 urad scan 320 urad 150urad channel May 26, 2007 Data Laser output Close to range Limit. 2 mrad scan data 4 mrad scan data

11. July 10, 2007 Data • On July 1, the laser zero was moved -1335 mrad to better center the laser on the proposed channel point. • On July 10 studies were conducted to rescan the areas found on May 26 to try to get a better picture of the channel and VR area. • On July 10 4 scans were made but no apparent channeling was seen or reproduced.

12. Angular motion Into the beam Goniometer Mechanics • The fact that scans were not reproducible made us look at the goniometer mechanics during the Aug to Oct shutdown to see if there was a problem. • It was found that for horizontal motion of 1mil (.025mm) produced an error of 200 urad in angle. • However, angular scan over the entire angular range for a fixed horizontal position were reproducible to 20urad. • We believed this was part of the problem on July 10 because between scans the horizontal motion was moved to put the crystal in closer to produce more signal.

13. Changed procedure for putting the crystal into beam sensitive to not changing the horizontal position. Rescanned and again found no obvious channeling point. November 16, 2007 Data

14. As a last attempt, it was thought that maybe there was an issue with beam hitting the crystal holder and generating noise. Conducted a study with the D49 target shadowing the crystal in front but the crystal is the leading edge. Again no apparent channeling was demonstrated. Protons ~ 1mm crystal E03H collimator D49 target November 30,2007 Data

15. 320 urad 150urad channel A New Look at all the Data • Since the data on May 26 had all the look of channeling, decided to look closer at data to see if data was in the noise. • We know that if channeling takes place there a correlation between T:LE033 and T:LEPIN. Therefore if take ABS(T:LE033-T:LE0PIN) and look for any large changes.

16. Reanalyze All Data Sets

17. Summary of Data Sets If the May 25 data indicated the channel and the laser was move for later scans by -1335 urad. The new channel point should be around -305 or -461 urad

18. Retracted Crystal CDF HALO LE033 LE0PIN Protons ~ 1mm crystal E03H collimator D49 target Comments about Noisy Losses • This noise has components of orbit motion and abort gap cleaning. It is also a function of generating halo with inefficiency in cleaning. • Saw similar magnitude noise with “O” shaped crystal. But the channel was much more obvious. • More general understanding of the halo profile is also needed.

19. Summary • Now that the channel has been identified, scans will need to be preformed to characterize this strip crystal. • Once the crystal channel and VR region is characterized, collimating the channeled will need to be completed as well as collimating the VR reflected beam. • Finally comparing the collimated (single plane) crystal beam compared to the tungsten target will need to be completed. • The next study period will add the Tevatron flying wire instrumentation to help generate better understanding on the channeled beam and hopefully the halo profile. • There will need to be some assessment from the experience of using a strip crystal for future choices of crystals used in Tevatron experiments.