1. 01/07/2005 SN 1 of 16 Esti mation of HOM Power in the Interaction Region of ILC Sasha Novokhatski Session “Beam RF Effects” ILC MDI Workshop SLAC January 7, 2005

2. 01/07/2005 SN 2 of 16 Central part of PEP-II IR

3. 01/07/2005 SN 3 of 16 Wake fields go through the fingers into vertex bellows cavity ~500 W [Stan Ecklund]

4. 01/07/2005 SN 4 of 16 Wake fields are absorbed in ceramic tiles of Q2-bellows ~10 kW [Stan Ecklund]

5. 01/07/2005 SN 5 of 16 IR Model Difficulties with 3-d calculations do not allow to do wake field calculations for very short bunches traveling in long structure We can use simplified 2-d model which already demonstrated good agreement with HOM measurements (Stan Ecklund) for PEP-II IR: –HOM power –Bunch length dependence

6. 01/07/2005 SN 6 of 16 PEP-II 2-d model and analog for ILC Transverse dimensions are two times smaller

7. 01/07/2005 SN 7 of 16 Wakes in IR at different time

8. 01/07/2005 SN 8 of 16 Wakes

9. 01/07/2005 SN 9 of 16 Wakes

10. 01/07/2005 SN 10 of 16 Loss factor for PEP-II IR Bunch length dependence changes from   (14-8 mm) to  -3/2 (6-2 mm)

11. 01/07/2005 SN 11 of 16 Loss factor for ILC IR Bunch length dependence   (0.3-0.1 mm)

12. 01/07/2005 SN 12 of 16 Shape of RF signal (wake potential)

13. 01/07/2005 SN 13 of 16 Comparison with wake in TESLA

14. 01/07/2005 SN 14 of 16 IP HOM Power

15. 01/07/2005 SN 15 of 16 ILC IP HOM Power for smaller bunch length

16. 01/07/2005 SN 16 of 16 Summary Electron and positron bunches produce electromagnetic fields (wakefields) in Interaction Region These fields travel for long distance and penetrate inside bellows, pumps and vacuum valves. Average power of these fields is not high, however pulse power can reach tens of kilowatt. More wake field studies are needed.