ATF Inrabeam Scattering Results：ATF束內(nèi)散射的結果

1、11/8/2021dr2003, jan. 27 at daresbury contents1) simple review of the measurement method2) comparison with simulation and theory3) summaryjunji urakawaand atf collaborationatf intrabeam scattering resultsmeasurement method to get the results we measured the horizontal emittance in the extraction lin

2、e using 5 wire scanners. energy spread was measured by thin screen monitor in the extraction line with large dispersion. vertical emittance was measured by 5 wire scanners in the extraction line, laser wire and sr interferometer in the damping ring. x-sr monitor indicates consistent results on trans

3、verse emittance. bunch length has been measured by streak camera with large statistical error. beam lifetime measurement has evaluated the emittance ratio with some assumptions.dr2003, jan. 27 at daresbury11/8/2021comparison measurements numerical comparison with sad comparison with simulation and t

4、heorydr2003, jan. 27 at daresburymeasurements dr2003, jan. 27 at daresburysr interferometerlaser wire in the ringmeasurementsenergy spread by screen monitorat the extraction linebunch length by streak camera in the ringnumerical comparison with saddr2003, jan. 27 at daresburynumerical comparison wit

5、h sad dr2003, jan. 27 at daresburycomparison with simulation and theory dr2003, jan. 27 at daresburycomparison with simulation and theorysummary vertical dispersion only, with (h)rms=5.6mm and ey0=4.0pm (solid). coupling dominated with k=0.33% (dashes). coupling dominated with k=1.2%, with the coulo

6、mb log artificially increased by a factor 1.75 (dotdash). same as ex. 2 but assuming ey measurement error, i.e. adding 0.9% of the measured (and splined) ex to the calculated ey (the dots). following is my suggestion (intention). reject the artificial increase. beam orbit tuning, dispersion and coup

7、ling correction have to do precisely. beam size measurement has to do quickly and precisely. improved tools will be prepared within 3 months.dr2003, jan. 27 at daresburynovel electron-beam diagnostic (laser wire )at st catherines college, oxford, englandjunji urakawa, kek, japan, july 10th 20031. de

8、velopment of laserwire beam profile monitor based on stable compton scattering in a fabry-perot optical cavity. (0.1mm(rms) position stability, 5mm(rms) beam collision.)2. future development3. conclusion ultra-low emittance electron beam is good for you.motivation linear colliders require nm-size be

9、ams damping rings produce ultra low emittance beams atf experiment at kekto demonstrate low emittance beam productiondevelop handling / monitoring techniquesstudy beam dynamics ( low emittance, multi-bunch )atf damping ring1.1 10-9 m rad ( horizontal emit.) 100 mm0.5 10-11 m rad ( vertical emit.) 7

10、mmbeam energy :1.28 gev intensity : 1.21010 e/ bunchnumber of bunches : single / multi (220bunches) (2.8ns spacing)need reliable beam size monitorsprinciple of laserwire monitorthin photon target (laserwire) transversely placed on the beam orbitscan across the electron beam“count” compton scattered

11、photons cw laserwire with optical cavityenhance laser power (high mirror reflectance high power gain )control laser waist size laser on/off for background subtractionimportant issues high intensity small waist sizereliable beam size monitor in damping ringnon-invasive methoddirect measurement of the

12、 beam sizedispersion negligible (straight section) multi-bunch beam (timing detection of gamma rays)work at almost zero current feature other monitors sr interferometer (arc)x-ray sr monitor (arc)wire scanner (ext)otr/odr (ext)1. laserwire2. detector and collimator3. data taking systemreplaced in 20

13、02 summer shutdowncavity modulewhole system mounted on movable tablemovable both vertical/horizontaltable position is monitored by laser position sensorhorizontal wirevertical wirefabry-perot high power gainnarrow resonance power inside cavity feedback controltransmission intensity = reference volta

14、ge 0.1 nm resolution servo systemcontrol cavity lengthpiezo actuatormonolithic elastic hingelaser specification cavity specificationhorizontal wire(vertical measurement)vertical wire(horizontal measurement)mirror front99.1 %99.8 %reflectanceend99.9 %99.9 %mirror curvature20 mm20 mmfinesse6201700powe

15、r gain6601300size (rms)5.67 0.1 m14.7 0.2 mrayleigh range760 m5100 mwavelength532 nmcw power300 mwlinewidth10 khz (1msec)lightwave series 142 diode-pumped solid state laser cw freq. doubled yag laserlaser-on: laser-off: 113 hz sinusoidal modulation background subtractionbackground 10khzlaser-on / la

16、ser-off measurementmodulate intra-cavity power (cavity length modulation)30% (time)85% of power (average)30% (time) 7.5% of power (average) compton scattering28.6 mev (max gamma energy)23.0 mev ( 0.2 mrad scattering angle ) gamma ray detector70 mm 70 mm 300 mm csi(pure) crystal2” photo-multiplier ti

17、me resolutionpmt signal leading edge0.56 nsec resolution (signal energy region)enough to separate 2.8ns spacing bunches energy spectrumsignal/background = 4 / 1 (vertical beamsize measurement)energy window (15mev 25mev) “counting” method no event pile-up (10khz rate / 2mhz ring revolution )energy ga

18、te and leading edge detectionbunch identification by gamma ray signal timing20 beam profiles (multi-bunch) at the same time single bunch emittance (mar 2003) bunch id by hit timing (bunch marker) laser on/off count ratealign collimatorsbeam based alignment for collimatorslocal orbit bump at laserwir

19、e position if needed scanning1 round trip for 1 profileautomatic scan vertical 10sec. for 1 position move 10 micron (6sec.) 6 min. for 1 scan error dominated by orbit drift horizontal 30sec for 1 position move 50 micron (10sec.) 15 min. for 1scan error dominated by statisticsvertical“bad data”longit

20、udinal laser profilelaserwire size = 5.67 0.1 m(laser divergence method)laserwire size = 5.46 0.2 m(fitting from focus scan)small waist size small rayleigh length change x-position and confirm laser profile laser has parabolic shapedispersion measurement by laserwire itselfchange ring rfscan beam by

21、 laserwiremeasure the beam position shiftvertical dispersion = 2.0 mm (almost negligible)horizontal dispersion = 2.0 mm (negligible) beta function at two collision pointsfor vertical measurement x= 9.81 m, y= 4.32 mfor horizontal measurement x= 7.83 m, y= 4.90 mbeamsize measurement as a function of

22、storage timestudy detector response after beam injectionhorizontalemittanceverticalemittancerecent results with calculated values on intra-beam scattering and pure inductive impedancebunchlengthenergyspreadhow to improve resolution?beam size : 5.5 mm laser waist size: 5.6 mm close to the resolution

23、limit possibilities stronger focusing fine tuning of cavity length sensitive to mirror geometries shorter rayleigh length shorter wave length high quality mirror high power / stable laser use higher transverse modeuse tem01 resonance mode in the optical cavity as a laserwirefactor 23 resolution impr

24、ovementinsensitive for beam orbit driftscan freegood resolution for small beam sizemisaligned laser injectionmode degeneration tem01/10mirror distortion to split these modesmirror distortionhigher order mode resonate in the cavitytransmitted light profiles of each modestable realization of higher or

25、der modestem00tem01tem02conclusionultra-low emittance electron beam is good for you.ultra-short bunched beams are good for my future r&d.now we are going to do nano-beam orbit handling with international collaboration. sub-nano meter and sub-100f second beam will be realized in the future. beam

26、diagnostics for above beam are necessary. idea of such diagnostics exists. however, present technologies are not mature. so, we continue r&d with challenging spirit for future linear collider project. 1. installation of 5 wire-scanners into atf linac2. improvement of temperature control of cooling water 3. sta