1. Experimental Study of the BEPC Ⅱ Backgrounds JIN Da-Peng IHEP, Beijing, China Representing the Backgrounds Study Group May 11, 2007, BEPC Ⅱ IMAC Meeting

2. Outline  Motivation  Radiation detectors arrangement  Preliminary results  Next to do

3. Motivation 1. Take means to protect the detectors from being damaged 2. Provide good environment for data taking BEPC Ⅱ is going well

4. Radiation Detectors Arrangement

5. Magnified View Fork Pipe Both Beams e- Beam On Mar. 27, 2007, 2# was moved to 5#

6. Detectors in the right places

7. Parameters of the Radiation Detectors PIN Diodes – 0.25nA/mrad·s -1 – Damage: 1~10nA/krad – Temp Dep: 1.11times/ o C – Accuracy: ~5mrad/s RadFETs – Range: 20,000rad – Accuracy: 1.5rad – Freq: 10min

8. Preliminary Results 1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP. 160nA 80nA

9. Preliminary Results 5# : 2.22m from the IP. 3000nA More than 1000nA

10. Preliminary Results 5# detector suffers much more radiation doses than the others, which is more than one fold. Dominated doses for 5# detector are from the electron beam. 1#, 2#, 3#, 4# : 75cm from the IP; (Both beams) 6# : 3.31m from the IP; (Upper stream of e-) 5# : 2.22m from the IP. (Upper stream of e-)

11. Preliminary Results Electron Beam Tuning 1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP.

12. Preliminary Results Electron Beam Tuning 5# : 2.22m from the IP.

13. Preliminary Results Electron Beam Tuning Dose rates during injections are much higher than steady runs for each detector. InjectionsSteady Runs Dose Rate (mrad/s) Tens to Hundrends 0.5 to about Ten Int. Dose (rad/day) About 100 rad (4#) to Several Thousands (5#)

14. Preliminary Results Positron Beam Tuning 1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP.

15. Preliminary Results Positron Beam Tuning 5# : 2.22m from the IP.

16. Preliminary Results Positron Beam Tuning 5# and 6# detectors suffers less doses. Vertical detectors suffers less doses. For the horizontal detectors 1# and 3#, Outer Ring(1#).GT. Inner Ring(3#)

17. Preliminary Results Double Beam Tuning 2# moved to 5#.

18. Preliminary Results Double Beam Tuning 2# moved to 5#.

19. Preliminary Results Double Beam Tuning 2# moved to 5#. Really, Dose Rate at the fork pipe (about 2.2m from the IP) is much higher.

20. Preliminary Results Int. Dose to the CsI Crystals 30cm 40cm 50cm 60cm

21. Preliminary Results Int. Dose to the CsI Crystals 40cm 50cm 60cm

22. Preliminary Results Int. Dose to the CsI Crystals The maximum Int. dose at the position of the inner most CsI crystals is about 10rads/day, which is about 10 times that of the design value. Injections bring much more doses. The total Int. dose from the electron beam is higher than that from the positron beam.

23. Preliminary Results Int. Dose at the fork pipe

24. In the previous measurement, the Int. dose is.GT. 3000rads/day, which is mainly due to e- injections. In some cases, one turn injections can bring hundrends to one thousand rads Int. doses.

25. Preliminary Results Beam Loss Monitors IP No. 48No. 72 BLMs are sensitive with charged particles e+ e-

26. Preliminary Results Beam Loss Monitors

30. Why so high dose?  The accelerator needs to be well tuned, since we have just started.  In the currently used vacuum chambers, the radius near the fork pipe is smaller than the design values and makes here the bottleneck of the storage ring.  Collimators not installed.

31. Next to do  Further understand the results from the PIN Diodes, FETs and BLMs;  Deal with the backgrounds seriously and push ahead the manufacture and installation of the collimators;  Your suggestions??? Thanks!