IMPEDANCE OF A ROUGH SURFACE VACUUM CHAMBER Alexander

IMPEDANCE OF A ROUGH SURFACE VACUUM CHAMBER Alexander Novokhatski ICFA mini-Workshop on “Electromagnetic wake fields and impedances in particle accelerators" Erice, Sicily 23 -28 April 2014 1 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Roughness? Standard unpolished surface Slice from measured “surface-1” along one of the “mountain ridges” (along extrusion, beam direction z) added to the beam pipe radius r of 1 mm. Measurement of “surface-1”. Extrusions are along mountain ridges (red). Vertical axis in mm; horizontal axes in pixels WAKE FIELDS DUE TO WALL ROUGHNESS FOR REALISTIC SURFACES* A. V. Fedotov#, I. Pinayev , BNL, Upton, NY 11973, USA A. Novokhatski, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA 2 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Very good surface (LCLS undulator chamber) Transmission electron microscopy of a polished aluminum sample 3 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Al oxide Wave number of a synchronous mode that has a phase velocity of speed of light in a metal tube (radius a) with a thin dielectric (e) layer (d) Wake potentials 4 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Slightly corrugated periodic structure 5 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Wake potentials of the tubes with corrugated periodic surface and with thin ceramic layer 6 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Synchronous mode. Properties. After passing a corrugated tube 7 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Wake shape (0. 3 mm bunch): almost single wave Wake Potential [V/p. C] Bunche shape 1500 25 20 1000 15 10 500 5 0 -2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 -5 -500 -15 -1000 -20 -1500 -25 12 mm 8 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Shape of the “long” wake potential 9 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Power spectrum 10 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Real and imaginary parts 11 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Tube horn 12 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Dipole modes 13 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

10 micron bunch in a rectangular chamber of in-vacuum undulator 14 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Random bumps 15 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Development of the Wake Field Pulse Time development of the rf-wake field pulse created by a 250 m bunch in a tube with 5 mm radius and an rms roughness depth of 50 m. 16 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Application. BNL Blue: bunch profile; red: wake potential for “surface-1”, r=1 mm. Loss factor k=16 V/p. C/m. WAKE FIELDS DUE TO WALL ROUGHNESS FOR REALISTIC SURFACES* A. V. Fedotov#, I. Pinayev , BNL, Upton, NY 11973, USA A. Novokhatski, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA Slice from measured “surface-1” along one of the “mountain ridges” (along extrusion, beam direction z) added to the beam pipe radius r of 1 mm. 17 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Rare bumps. Inductive wake potential. 18 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Bunch 10 micron 19 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Rare bumps 20 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Spectrum 21 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Other approach. G. Stupakov. 22 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

Measurements 23 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014

When roughness is important? When effect from wake fields due to roughness comparable with resistive-wall wake fields 24 OPERATED BY STANFORD UNIVERSITY FOR THE U. S. DEPT. OF ENERGY SN 04/26/2014