1 Studies of electron cooling at DESY K. Balewski, R. Brinkmann, Ya. Derbenev, Yu. Martirosyan, K. Flöttmann, P. Wesolowski DESY M. Gentner, D. Husmann, C. Steier Uni Bonn

2 Overview Introduction cooler scheme medium energy cooling in PETRA high energy cooling in HERA concluding remarks

3 Future options for HERA –electron ion collisions: to get required luminosity increase of ion beam brightness necessary –collisions of electrons with polarized protons or deuterons: acceleration of polarized protons can be eased by decreasing the vertical beam size Introduction Idea: decrease emittance (especially vertical) of hadron beam with electron cooling

4 Cooler Scheme Cooling of ions in two stages 1) precooling at medium energy (8-20 GeV) 2) cooling at high energy ( GeV) mainly to preserve high beam quality Cooling of pol. Protons: cooling at medium energy (8 GeV) sufficient

5 Cooler Scheme Why cooling in two stages?

6

7 Medium energy cooling in PETRA general layout

8 Medium energy cooling: Non magnetized cooler

9 Medium energy cooling PETRA layout of debuncher

10 Medium energy cooling in PETRA magnetized cooler Simulation results: Q = 5 nC E=9MeV  N (1  ) < 2 mm mrad  E = 25 keV  z = 17 mm

11 Medium energy cooling in PETRA matching between solenoids Problems : nonlinear fields, chromatic effects, space charge, rf defocusing

12 Medium energy cooling in PETRA matching between solenoids

13 Medium energy cooling in PETRA matching between solenoids

14 Medium energy cooling in PETRA rf gun - alternative to thermionic gun 1 1/2 208 MHz cw cavities max. gradient: 5 MV/m Simulation results: E = 1 MeV Q = 5 nC  N = 3 mm mrad  E = 7 keV  z = 20 mm

15 Medium energy cooling in PETRA layout of recirculator Cooler solenoid Combined function bendings n=1/2 QD1 QD QF1 QF QF1QD m 0.7m Simulation including non-linear, space charge and chromatic effects confirm preservation of electron beam quality

16 High energy e-cooling HERA layout of cooler ring Cooling section: high beta insertion (L=120m) arcs: diameter 16m (tunnel 5.2m)  sextupol strength wiggler section: dispersion free, 37 wigglers, B = 1T tuning section: adjusting tunes, coupling - rf cavities

17 High energy cooling: optics of cooler ring

18 High energy cooling in HERA Tolerances, instabilities, Touschek effect etc. seems to be O.K.

19 High energy e-cooling HERA linac vs. cooler ring Storage ring is the right choice in our case

20 conclusions Medium energy cooling –pre-cooling with non magnetized cooler of heavy ions o.k. –Magnetized cooler problems with solenoid field matching high energy cooling –cooling with cooler storage ring of heavy ions o.k. –cooling of protons very difficult –pre-cooling of heavy ions highly desirable