ATFIntrabeamScatteringResults：ATF束内散射的结果37张精选课件

1、Measurement Method to get the ResultsWe measured the horizontal emittance in the extraction line 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

2、and SR interferometer in the damping ring.X-SR monitor indicates consistent results on transverse emittance.Bunch length has been measured by streak camera with large statistical error.Beam lifetime measurement has evaluated the emittance ratio with some assumptions.DR2019, Jan. 27 at Daresbury第1页，共

3、37页。Comparison Measurements Numerical Comparison with SAD Comparison with Simulation and TheoryDR2019, Jan. 27 at Daresbury第2页，共37页。Measurements DR2019, Jan. 27 at DaresburySR InterferometerLaser Wire in the ring第3页，共37页。MeasurementsEnergy Spread by Screen Monitorat the Extraction LineBunch Length b

4、y Streak Camera in the Ring第4页，共37页。Numerical Comparison with SADDR2019, Jan. 27 at Daresbury第5页，共37页。Numerical Comparison with SAD DR2019, Jan. 27 at Daresbury第6页，共37页。Comparison with Simulation and Theory DR2019, Jan. 27 at Daresbury第7页，共37页。Comparison with Simulation and Theory第8页，共37页。SummaryVer

5、tical 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 Coulomb 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 spline

6、d) ex to the calculated ey (the dots). Following is my suggestion (intention).Reject the artificial increase.Beam orbit tuning, dispersion and coupling correction have to do precisely.Beam Size Measurement has to do quickly and precisely.Improved tools will be prepared within 3 months.DR2019, Jan. 2

7、7 at Daresbury第9页，共37页。Novel Electron-Beam Diagnostic (Laser Wire )at St Catherines College, Oxford, EnglandJunji Urakawa, KEK, Japan, July 10th 20191. Development of laserwire beam profile monitor based on stable Compton scattering in a Fabry-Perot optical cavity. (0.1mm(rms) position stability, 5m

8、m(rms) beam collision.)2. Future development3. Conclusion Ultra-low emittance electron beam is good for you.第10页，共37页。Introduction to laserwiremotivation Linear Colliders require nm-size beamsDamping rings produce ultra low emittance beamsATF experiment at KEKto demonstrate low emittance beam produc

9、tiondevelop 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 mmbeam energy :1.28 GeV intensity : 1.21010 e/ bunchnumber of bunches : single / multi (220bunches) (2.8ns spacin

10、g)need reliable beam size monitors第11页，共37页。Introductionprinciple of laserwire monitorthin photon target (laserwire) transversely placed on the beam orbitscan across the electron beam“count” Compton scattered photons CW laserwire with optical cavityenhance laser power (high mirror reflectance high p

11、ower gain )control laser waist size laser on/off for background subtractionImportant issues high intensity small waist size第12页，共37页。reliable beam size monitor in Damping ringnon-invasive methoddirect measurement of the beam sizedispersion negligible (straight section) multi-bunch beam (timing detec

12、tion of gamma rays)work at almost zero current Introductionfeature other monitors SR interferometer (arc)X-ray SR monitor (arc)wire scanner (ext)OTR/ODR (ext)第13页，共37页。Experimental setup1. laserwire2. detector and collimator3. data taking system第14页，共37页。Chamber systemreplaced in 2019 summer shutdow

13、ncavity module第15页，共37页。Opticswhole system mounted on movable tablemovable both vertical/horizontaltable position is monitored by laser position sensor第16页，共37页。Laserwire setuphorizontal wirevertical wire第17页，共37页。Cavity resonanceFabry-Perot high power gainnarrow resonancepower inside cavity第18页，共37

14、页。Cavity controlfeedback controltransmission intensity = reference voltage 0.1 nm resolutionservo systemcontrol cavity lengthpiezo actuatormonolithic elastic hinge第19页，共37页。Optical cavity and laserlaser specificationcavity specificationhorizontal wire(vertical measurement)vertical wire(horizontal me

15、asurement)mirror front99.1 %99.8 %reflectanceend99.9 %99.9 %mirror curvature20 mm20 mmfinesse6201700power 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 la

16、ser第20页，共37页。Laser power modulationLaser-ON: Laser-OFF: 113 Hz sinusoidal modulationbackground subtractionbackground 10kHzLaser-ON / Laser-OFF measurementmodulate intra-cavity power (cavity length modulation)30% (time)85% of power (average)30% (time) 7.5% of power (average)第21页，共37页。DetectorCompton

17、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-multipliertime resolutionPMT signal leading edge0.56 nsec resolution (signal energy region)enough to separate 2.8ns spacing bunches第22页，共37页。Compton scattering s

18、ignalEnergy spectrumsignal/background = 4 / 1 (vertical beamsize measurement)energy window (15MeV 25MeV)“counting” method no event pile-up (10kHz rate / 2MHz ring revolution )energy gate and leading edge detectionbunch identification by gamma ray signal timing第23页，共37页。Signal processing20 beam profi

19、les (multi-bunch) at the same timesingle bunch emittance (Mar 2019)bunch ID by hit timing (bunch marker)laser ON/OFF count rate第24页，共37页。Data takingalign collimatorsbeam based alignment for collimatorslocal orbit bump at laserwire position if neededscanning1 round trip for 1 profileautomatic scan ve

20、rtical 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”第25页，共37页。Laser waist measurementlongitudinal laser profilelaserwire size = 5.

21、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 shape第26页，共37页。Additional datadispersion measurement by laserwire itselfchange Ring RFscan beam by laserwiremeas

22、ure 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 m第27页，共37页。Beam damping measurementbeamsize measuremen

23、t as a function of storage timestudy detector response after beam injection第28页，共37页。HorizontalEmittanceVerticalEmittanceRecent Results with calculated values on intra-beam scattering and pure inductive impedanceBunchLengthEnergySpread第29页，共37页。Future planHow to improve resolution?beam size : 5.5 mm

24、 laser waist size: 5.6 mm close to the resolution limitpossibilitiesstronger focusingfine tuning of cavity lengthsensitive to mirror geometriesshorter Rayleigh lengthshorter wave lengthhigh quality mirrorhigh power / stable laseruse higher transverse mode第30页，共37页。Twin peaks laserwireuse TEM01 reson

25、ance mode in the optical cavity as a laserwirefactor 23 resolution improvementinsensitive for beam orbit driftscan freegood resolution for small beam size第31页，共37页。Higher mode resonancesmisaligned laser injectionmode degeneration TEM01/10mirror distortion to split these modesmirror distortionhigher

26、order mode resonate in the cavitytransmitted light profiles of each mode第32页，共37页。Higher mode test experimentstable realization of higher order modesTEM00TEM01TEM02第33页，共37页。ConclusionUltra-low emittance electron beam is good for you.Ultra-short bunched beams are good for my future R&D.Now we are go

27、ing to do nano-beam orbit handling with international collaboration. Sub-nano meter and sub-100f second beam will be realized in the future. Beam 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. 第34页，共37页。Installation of 5 wire-scanners into ATF LinacImprove