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

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

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. start  time Landau damping of betatron motion displacement

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. start  time Landau damping of betatron motion displacement

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. start  time Landau damping of betatron motion displacement 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 T S

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Betatron tune shift with chromaticity With synchrotron oscillation Averaged tune shift over T S   = 0.047%  0 = 5  1 = 0 time (ms) Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms tune spread

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 0.2 ms

Chromatic Tune Spread Chromaticity modulation With synchrotron oscillation Averaged tune shift over T S time (ms)   = 0.047%  0 = 0  1 = 1 Coherent oscillation amplitude T S = 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?

CSR 非 CSR  CSR  放射パワー :P バンチ内電子数 :N single bunch 1mA  N=2.5 x10 9 electrons 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 Coherent Synchrotron Radiation (CSR)

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-AB (2004)] Longitudinal movement after the deflection [Y.Shoji, NIMA in press]

H/L coupling can produce CSR Stored electron energy0.5 GeV  p Revolution frequency2525 kHz Natural energy spread % L damping time96 ms fs15 kHz AC chromaticity amp 10 Natural emittance7.5 nm H at the observation point0.2 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 energy1 GeV Dispersion at AC60.73 m Beta func. at AC617/13 m Betatron tune6.2, 2.2 DC chromaticity33 Synch. osc. frequency5 kHz Natural energy spread0.047% Rad. damping time22 ms AC6

AC Sextupole magnet system ( T. Nakamura, K. Kumagai, Y. Shoji, T. Ohshima, …MT-20, 2007) Pole length0.15m Bore diameter80 mm Yoke material0.35 mm Si steel Coil turn1 turn/pole Operation frequency4 – 6 kHz Drive current300A peak Field strength36 T/m 2 Modulation amplitude  /1.25 Damping time0.21/0.27 ms (Synchrotron osci. period0.2ms) Now trying to reduce Eddy-current loss at the inner coil Measurement at NS – Not yet started

Coherent Oscillation Damping single kicksinusoidal deflection H / V  0 =1.1 / 0.9  L = 1.3 / 1.6 ms  L = 0.84 / 1.1 ms  L = 0.42 / 0.54 ms  1 = 0.82 / 0.63 ms  RAD =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 Measurement at NS – Not yet started

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.