Possibility of narrow-band THz CSR by means of transient H/ L coupling

Possibility of narrow-band THz CSR by means of transient H/L coupling NewSUBARU, LASTI, University of Hyogo Y. Shoji

Today’s Lines • 1 Landau damping by the chromaticity modulation • ;T. Nakamura, et al., IPAC’10 • 2 Coherent Synchrotron Radiation (CSR) from wavy bunch • ; Y. Shoji, Phys. Rev. ST-AB13 060702 (2010) • 3 Transient H/L coupling • ; Y. Shoji, NIMA in press (available on-line) • ; 2010日本物理学会 • 4 Possibility of CSR emission by means of the coupling • New Idea !

Landau damping of betatron motion Suppose that particles in a bunch have tune variation (spread). After many revolutions, they oscillate with different phases. Then the oscillation amplitude of the average (coherent osci.) becomes smaller. displacement start time

Landau damping of betatron motion Suppose that particles in a bunch have tune variation (spread). After many revolutions, they oscillate with different phases. Then the oscillation amplitude of the average (coherent osci.) becomes smaller. displacement start time It suppresses the growth of the oscillation.  suppression of any transverse instability

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over TS

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over TS sd =0.047% x0= 5 x1= 0 Coherent oscillation amplitude time (ms) TS = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over TS tune spread sd =0.047% x0= 0 x1= 1 Coherent oscillation amplitude time (ms) TS = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over TS sd =0.047% x0= 0 x1= 1 Coherent oscillation amplitude time (ms) TS = 0.2 ms

Generation of spatial wavy bunch The wavy structure is instantaneously produced. Its wave number increases with time. Is there any way to utilize this structure?

Coherent Synchrotron Radiation (CSR) CSR 非CSR  CSR  放射パワー:P バンチ内電子数:N single bunch 1mA  N=2.5 x109electrons Radiation from N electrons in a bunch Form factor ; f

Coherent Synchrotron Radiation (CSR) Modulation and Radiation No modulation Spatial modulation Density modulation Vertical spatial modulation --> Vertically polarized radiation

Generation of spatial wavy bunch

Generation of spatial wavy bunch Transverse coherent oscillation is damped by the longitudinal radiation excitation with finite chromaticity (Is this a Landau damping?)

Generation of spatial wavy bunch

H/L coupling can produce CSR Is it really impossible to generate CSR by horizontal deflection? Horizontal kick + Chromaticity modulation  Horizontal spatial wavy structure At dispersive locations Longitudinal wavy structure = Density modulation CSR Horizontal kick also works to generate CSR!

Transient H/L coupling A particle circulating around a ring with horizontal betatron motion runs inner side and outer side of bending magnets  Transient longitudinal oscillation

Transient H/L coupling A particle circulating around a ring with horizontal betatron motion runs inner side and outer side of bending magnets  Transient longitudinal oscillation Simple analytical formulae [Y.Shoji, PR ST-AB7 090703(2004)] Longitudinal movement after the deflection [Y.Shoji, NIMA in press]

H/L coupling can produce CSR Stored electron energy 0.5 GeV Ap 0.0013 Revolution frequency 2525 kHz Natural energy spread 0.024 % L damping time 96 ms fs15 kHz AC chromaticity amp 10 Natural emittance 7.5 nm H at the observation point 0.2 m Horizontal deflection 150 nm t = 6.5 Ts

Measurement at NS – Not yet started Non-achromatic lattice (Y. Shoji, 2005 Ann. Meeting of PASJ) Electron energy 1 GeV Dispersion at AC6 0.73 m Beta func. at AC6 17/13 m Betatron tune 6.2, 2.2 DC chromaticity 33 Synch. osc. frequency 5 kHz Natural energy spread 0.047% Rad. damping time 22 ms AC6

Measurement at NS – Not yet started AC Sextupole magnet system ( T. Nakamura, K. Kumagai, Y. Shoji, T. Ohshima, … MT-20, 2007) Pole length 0.15m Bore diameter 80 mm Yoke material 0.35 mm Si steel Coil turn 1 turn/pole Operation frequency 4 – 6 kHz Drive current 300A peak Field strength 36 T/m2 Modulation amplitude x1 1.63/1.25 Damping time 0.21/0.27 ms (Synchrotron osci. period 0.2ms) Now trying to reduce Eddy-current loss at the inner coil

Measurement at NS – Not yet started Coherent Oscillation Damping single kick sinusoidal deflection H / V x0=1.1 / 0.9 tL= 1.3 / 1.6 ms tL =0.84 / 1.1 ms tL =0.42 / 0.54 ms x1 =0.82 / 0.63 ms tRAD=22 ms; Ts=0.2 ms

Measurement at NS – Not yet started Multi-function Corrector Magnet System ( Y. Shoji, … MT-21, 2009, IPAC’10) Can afford to produce Skew quadrupole Skew sextupole Normal octupole 4 magnets at the dispersion sections 2 magnets at the straight section

CLOSING COMMENT We are preparing for the demonstration, but not yet started. We hope someone, who is interested in, will come to join us. Thank you for your attention.

Possibility of narrow-band THz CSR by means of transient H/ L coupling