Status of Coherent Radiation Beamline at KURRI-LINAC Toshiharu - - PowerPoint PPT Presentation

CSR Workshop Sep.24, 2007, UVSOR

Toshiharu TAKAHASHI Research Reactor Institute, Kyoto University (Japan)

Status of Coherent Radiation Beamline at KURRI-LINAC

Outline of KURRI-LINAC Specifications of the beamline

(including coherence of CTR)

Spectroscopic demonstrations

• n the beamline

Outline

Outline of KURRI-LINAC

RF: L-band (1.3GHz) Energy: 40 MeV It was constructed in 1964 for pulsed neutron source. (Multi-bunch operation) Pulse width: 2ns～4µs

(Applied Radiation, USA)

Beam power: Max. 10kW (30MeV, 330µA) Peak current: Max. 8A Research field (collaboration research program)

Nuclear data with TOF Isotope production Electron irradiation Coherent radiation

Operation time: 2,700Hr (in 2006)

10 weeks user-time/year since 1991

Linac-based coherent radiation disadvantage

Single-user

advantages

Various types of coherent radiation are available.

(synchrotron, transition, diffraction, Smith-Purcell, Cherenkov)

Interaction between electron beam and medium is available. High peak-power (the high amount of charge in a bunch～several nC)

A c c e l e r a t

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R

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E x p e r i m e n t a l R

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S h i e l d W a l l f r

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a n d L i n a c e l e c t r

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b e a m T i w i n d

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I n t e r f e r

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e t e r A l f

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h r

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a t

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Schematic diagram of the beamline

CSR is also available with a bending magnet.

Parallel beam (φ15 cm) spherical mirror spherical mirror CTR CTR

Photograph around the emission point

Electron beam CTR flat Al-foil

(Target Room)

Spectrometers and detectors

spectrometers

Grating type monochromator (Czerny-Turner type) Martin-Puplett type Interferometer (step scan)

detectors

Si bolometer (Liquid-helium-cooled ) InSb bolometer (Liquid-helium-cooled ) Diode detector monochromatic light high dynamic range broadband spectrum high sensitivity, low noise VBW1kHz high sensitivity, low noise VBW1MHz narrowband fast detector VBW1GHz

signal acquisition

Lock-in amplifier Fast gated integrator for pulsed light source of small duty ratio

(home-made)

Photograph of spectrometer

Martin-Puplett type interferometer Grating type monochromator (Czerny-Turner type)

(The grating is replaced by a flat mirror under the interferometer mode.)

Stability of intensity

20 40 60 80 TIME (min.) 0.01 0.02 VOLTAGE (V)

Long-time stability Pulse stability within ±1% Si bolometer on the interferogram Lock-in Amplifier (Time const.:0.1s) Si bolometer on the interferogram Repetition rate: 46Hz Oscilloscope: envelope mode

Correction of fluctuation

If the intensity fluctuates due to the trouble of the linac …..

1.5 2.0 2.5 VOLTAGE (a)observed interferogram (b)beam current (c)monitor (d)corrected interferogram

Figure 3 Utilizati

• n of coherent ....

T akahashi et al.

0.5 1.0 1.5 CURRENT 1 2 3 VOLTAGE

• 4
• 2

2 4 OPTICAL PA TH DIFFERENCE (cm) 1.5 2.0 2.5 VOLTAGE

detector for monitoring fluctuation after correction before correction

Temporal structure of CTR

enlarged Macro-pulse width: 47ns Diode detector 770ps (1.3GHz) W-band 75-110GHz

Interferogram of large optical path difference

10 20 30 40 50 OPTICAL PATH DIFFERENCE (cm) 0.02 0.04 OUTPUT VOLT AGE (V) 0cm 23cm 46cm

cross-correlation autocorrelation cross-correlation

Inter-bunch distance

CTR form successive bunches

1 2 3 4 5 6 7 WAVENUMBER (cm-1) 0.00 0.05 0.10 0.15 INTENSITY (arb. units) max.OPD=54.2cm max.OPD=5cm (∆ν=0.018cm-1) (∆ν=0.20cm

• 1)

continuous spectrum：Δν＞f RF／c(cm-1)

low resolution high resolution Restriction on continuous spectrum Restriction on delay time in the time resolved measurement Demerit

• f multi-bunch

The single bunch operation is needed.

0.043cm-1 for 1.3GHz

Generation of single bunch

Sub-harmonic pre-buncher

• 10
• 5

5 10 OPTICAL PATH DIFFERENCE (mm) 0.05 0.1 0.15 0.2 OUTPUT VOLTAGE (V) 230 235 240 245 250

Waveform of CTR （diode detector） Interferogram of CTR (Si bolometer)

degree of impurity ～ 1.5%

High-speed avalanche-type pulser Development and install on electron injector no space expensive

autocorrelation cross-correlation 770ps

Spectrum of CTR

(acceptance angle: 70mrad) equipped on the interferometer (100W; aperture φ10)

Pure rotational spectrum of N2O gas

5 10 15 WAVENUMBER (cm-1) 0.5 1 1.5 2 ENERGY (meV) 1 TRANSMISSIVITY

J=2 J=3 J=4 J=5 J=6 J=7 J=8 J=9 J=10 J=11 J=12 J=13 J=14 J=15 J=16 J=17 J=18 J=19 J=20

Resolution: 0.2cm-1 Optical path length in N2O: 9.3m Pressure: 2×104 Pa

T.Takahashi et al. Rev.Sci.Instrum., 69(1998)3770

Absorption spectrum of OH-ion in NaCl

1 2 3 4 5 6 7 8 9

WA VENUMBER (cm-1)

2 4 6 8 10

ABSORPTION COEFFICIENT (cm-1) NaCl(0.5mol%) t=5.7mm 4.22K 1.46K

1.56cm

• 1(calc.)

1.88cm

• 1(calc.)

1.40cm

• 1(exp.)

1.95cm

• 1(exp.)

Cl Na HO (collaboration research with Tohoku Univ.) Light-pipe type Cryostat (1.4K～4.2K)

MM-wave magneto-spectroscopy

Electron spin resonance of Mn ions in RbMn0.3Mg0.7F3

1.2 1.0 0.8 0.6 0.4

Transmission

5.0 4.5 4.0 3.5 3.0 2.5 2.0

B (T)

FWHM = 0.235 T 4.133 T

77 K λ=2.5 mm

Repetition rate: 17 Hz Time delay

synchronization

59 ms

Macro pulse ~ 4 µs B ~ 1 ms CTR Capacitor bank: 533×658×1234mm3

• Max. 20T

Coil: outer diameter: 20-30mm, length: 10-30mm, bore size: 3-6mm

Portable pulsed magnet

(collaboration research with Okayama Univ.)

Y.H.Matsuda et al. Physica B 346-347(2004)519

MM-wave Pulseradiolysis

• ptical delay

0～770ps for multi-bunch CTR

electron beam CTR (at sample position) 10Lb (7.7ns)

For single-bunch a new idea of layout is necessary.

Summary

Optical conductivity of superionic conductors (collaboration research with Tohoku Gakuin Univ.) Optical properties of water and polymeric materials under γ-ray irradiation (collaboration research with Osaka Prefecture Univ.) Development of pulseradilysis system

Researches in progress KURRI-LINAC has been upgraded for coherent radiation. stabilization, generation of single-bunch beam Several spectroscopic researches has been demonstrated.