optical cavity r&d around kek-atf
DESCRIPTION
Optical Cavity R&D around KEK-ATF. T.Takahashi Hiroshima Univ. Nov. 2008 LCWS08 at Chicago. an idea. Klemiz , Monig. Experimental R/D in ATF. Hiroshima- Waseda -Kyoto-IHEP-KEK. Make a fist prototype 2-mirror cavity. L cav = 420 mm. Put it in ATF ring. accuracy ~ 0.8 m m. - PowerPoint PPT PresentationTRANSCRIPT
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T.Takahashi Hiroshima
Optical Cavity R&D around KEK-ATF
T.Takahashi Hiroshima Univ. Nov. 2008
LCWS08at Chicago
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an ideaKlemiz, Monig
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Experimental R/D in ATF
.
Make a fist prototype 2-mirror cavity
Put it in ATF ring
Hiroshima-Waseda-Kyoto-IHEP-KEK
Lcav = 420 mm
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4
Set up at KEK-ATF
accuracy ~ 0.8mm
electron beam
Horizontal
Vertical
Optical cavity
Cavity position is moved
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Lcav = n Lcav = m Llaser
Laser freq = Ring RF
Feedback to Achieve 3 Conditions
mode locked laser
pulse stacking cavity
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6
The appearance of light resonance signal
Reflected light
Transmitted light
the optical cavity is on resonant
Transmitted light
Mirror reflectivity : 99.6%
Mode locked laser
(Photo diode)
PD
time (ms)Continued to change the length of the external cavity.
1ms
0.7nm ~l/enhacement/p
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PhaseDetector
Piezo
Piezo
PD
Ref-light
StackingCavity
Laser
PID
RingRFke
ep r
eso
nan
ce
sync. to Acc.laser light
pulses
offset
(Sakaue)
Cross-feedback=Closed loop
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R. Cizeron
e- be
am
laser beam
4-mirror cavity
2-mirror cavity
Spot size = 30 umEnhance = 1000
Spot size = 10 umEnhance = 10000
2-mirror-cav to 4-mirror-cav.
difficult to achieve both high enhancement and small spot
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α
2D configuration
3D configurationFocal points for horizontal and vertical are not same
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R&D of 4 mirrors cavity started
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Two resonat peaks due to geometrical phase
Right LeftLinear
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Summary and prospects• photon generation by Laser pulse stacking cavity /
accelerator has been demonstrated both for– Polarized electron source (PosiPol)– hard x ray generation (LUCX)
• A project for x ray source has started• All projects going to 4 mirror ring cavity
– Technique with Ring cavity and e-beam will be accumulated in next 3-4year
• Specific study is for 100 m long cavity is necessary– supporting 1m scale mirrors– adaptive optics to maintain phase front– Feed back experiment to cavity design
• 3 Dimensional cavity• polarization
T.Takahashi Hiroshima
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Optical Cavity R&D around ATF
• O(10MeV) gs for Compton Based Polarized Positron source.
• Hard X ray (~30keV) sources – LUCX project
• New 5 year project – Compact X ray source w/ SRF electron
accelerator and pulse stacking cavity.
T.Takahashi Hiroshima
Accumulating technique and experiences w/ cavity and accelerators.
ring cavities are being planned as next step
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data summarybunch/train
current[mA]
StackedLaser power[W]
gs/crossing exectationnormarizedgs/A/W
Normalized g yield seems to decrease as # bunches/train goes up
Bunch (size, timing) fluctuation in the ATF suspected