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Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

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Page 1: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Optical diagnostics for beam halo

(I) Coronagraph

(II) OTR halo monitor for J-PARC

T. Mitsuhashi, KEK

Page 2: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

(I) Coronagraph

Page 3: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Everything was start with astronomer’s dream……

Eclipse is rare phenomena, and only few second is available for observation of sun corona, prominence etc.

Artificial eclipse was dream of astronomers, but……..

Page 4: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Why we can see sun corona by eclipse without diffraction fringe?

Because no aperture between sun and moon.It means no diffraction source in eclipse.

Question is can we make same system with artificial way?

Page 5: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Diffraction source aperture is in here.

Compare two setup, eclipse and artificial eclipse.

Answer is to eliminate diffraction fringe from aperture. …but how????

Page 6: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Objective lens

Magnifier lens

Opaque disk to block glare of central image

Observation with normal telescope

Diffraction fringes vs. halo

Page 7: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Diffraction fringesGaussian profile

Convolution between diffraction fringes and object profile

Page 8: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Diffraction makes fringes surrounding from the central beam image.

Intensity of diffraction fringes are in the range of 10-2 -10-3 of the peak intensity.(electron beam)

The diffraction fringes disturb observation of week object corona surrounding which has intensity range of 10-5 -10-6 of bright sun sphere.

Page 9: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Diffraction fringesGaussian profile

Convolution between diffraction fringes and beam profile

Blocked by opaque disk

Page 10: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

The coronagraph to observe sun corona

Developed by B.F.Lyot in 1934 for a observation of sun corona by artificial eclipse.

Special telescope having a “re-diffraction system” to eliminate a diffraction fringe.

Page 11: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Optical system of Lyot’s corona graph

Objective lens

Field lens

Baffle plate (Lyot stop)

Relay lens

Opaque disk

Anti-reflection disk

Baffle plates to reduce reflection

Page 12: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Re-diffraction optics system to eliminate the diffraction fringe

Page 13: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Opaque disk

Lyot stop

Re-diffraction optics systemOpaque disk

Field lens

Objective lens

Re-diffraction optical system

Page 14: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Objective lens with anti-reflection disk to block reflected light from opaque disk

Page 15: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

R

r

The integration performs r and R

r: radius of Anti-reflection disk

R: radius of objective lens aperture

Objective lens diffraction

Page 16: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Disturbance of light F( )x on opaque disk is given by;

dx2i

exp)(fi

1)(F

R

robjobj ff

In here f( )h is disturbance of light on objective lens.

Page 17: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Opaque disk

Lyot stop

Re-diffraction optics systemOpaque disk

Field lens

Objective lens

Re-diffraction optical system

Function of the field lens : make a image of objective lens aperture onto Lyot stop

Page 18: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

x1

x2

The integration performs x1 and x1

x1: radius of field lens

x2: radius of opaque disk

Field lens diffraction

Page 19: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

d

x2iexp)(F

i

1)x(u

2

1fieldfield ff

Disturbance of light on Lyot’s stop by re-diffraction system is given by;

Page 20: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Geometrical image of the aperture of objective lens

Intensity distribution of diffraction fringes on focus plane of field lens

Page 21: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Block the re-diffraction fringes

Page 22: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Opaque disk

Lyot stop

Re-diffraction optics systemOpaque disk

Field lens

Objective lens

Re-diffraction optical system

Function of the field lens : make a image of objective lens aperture onto Lyot stop Blocking diffraction fringe by

Relay lens to relay corona image onto final focus point

Page 23: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Lyot stop Blocking diffraction fringe by

Relay of corona image to final focus point

Page 24: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

x1

The integration performs h1

h1: radius of Lyot stop

Relay lens diffraction

Page 25: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

dxx2i

exp)x(ui

1)(V

1

0

relayrelay ff

Disturbance of light on final focus point V(x) is given by;

U(x) is still not 0 inside of relay lens pupil!

Page 26: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Background in classical coronagraph

Re-diffraction intensity on the Lyot stop

Diffraction fringe exists here

This leakage of the diffraction fringe can make background level 10-8 (depends on Lyot stop condition).

Page 27: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Observation of the sun corona by coronagraph

Page 28: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Front view of the coronagraph

Photographs of coronagraph

Page 29: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Objective lens with anti-reflection disk to block reflected light from opaque disk

Page 30: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Field lens

Lyot’s stop

View from the back side

Page 31: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Fast gated camera set on the final focusing point

Page 32: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Zoom up of opaque disk.Shape is cone and top-angle is 90º

Page 33: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Opaque disk assembly

Page 34: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Background source in coronagraph

1.Scattering by defects on the lens surface (inside) such as scratches and digs.

2. Scattering from the optical components (mirrors) near by coronagraph.

3. Reflections in inside wall of the coronagraph.

4. Scattering from dust in air.

Page 35: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

1.Scattering by defects on the lens surface (inside) such as scratches and digs.

2. Scattering from the optical components (mirrors) near by coronagraph.

3. Reflections in inside wall of the coronagraph. Cover the inside wall with a flock paper (light trapping material).

4. Scattering from dust in air. Use the coronagraph in clean room.

Page 36: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Scattering from defects on the lens surface such as scratches and digs.With normal optical polishing, for example S&D 60/40 scattered light intensity : about 10-3 times of input light intensity.

Page 37: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

S&D 60/40 surface of the glass

5mm

Page 38: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Result of careful optical polishing for the objective lens

5mm

Page 39: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Scattering from the optical components (mirrors) between source point and coronagraph.

Page 40: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

29401100

SR beam

electron beam orbit

Set up of SR monitor at the Photon factory

mirror

mirror

2900

source point

Scattering from Be-mirror is about 5x10-7

Scattering from the mirror which set at 2m in front of coronagraph is about 6x10-5

coronagraph

Page 41: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Scattering background from mirrors near by coronagraph will not acceptable!

Use same quality of optical polishing for mirrors!

Page 42: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Observation of beam halo at the Photon Factory, KEK

Page 43: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Beam profile

Page 44: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Beam halo

Page 45: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Intentionally spread some dust on the mirror in 2m front of the coronagraph

Page 46: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Diffraction tail observed without Lyot’s stop

Entrance pupil is intentionally rotated by 30º to recognize diffraction tail easily.

30°

Page 47: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

10-5

0.0001

0.001

0.01

0.1

0 2 4 6 8 10 12 14

holizontal beam size in s

Diffraction fringe

Beam halo

Comparison between beam tail and diffraction tail

Page 48: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Move the opaque disk slightly to show the edge of central beam image (diamond ring!)

Page 49: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

65.8mA 61.4mA 54.3mA

45.5mA 35.5mA 396.8mAMulti-bunch bunch current 1.42mA

Beam tail images in the single bunch operation at the KEK PF measured at different current

Page 50: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Single bunch 65.8mAExposure time of CCD : 3msec

Exposure time of CCD : 100msec

Intensity in here : 2.05x10-4 of peak intensity

2.55x10-6

Background leavel : about 6x10-7

Halo in deep outside

Observation for the more out side

Page 51: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Strong tail

Weak tail in outside

1 101 201 301 401 501

1 101 201 301 401 501

x 33

Page 52: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Conclusions

• The coronagraph was designed and constructed for the observation of weak object (such as tail and halo) surrounding from central glare of the beam.

• Optical polish of the objective lens is key point to realize good S/N ratio, and we reached ratio of background to peak intensity 6x10-7.

• Spatial resolution is about 50mm (depends opening of optics)• By using the coronagraph, we observe beam tail at

the photon factory storage ring. As results; 1. a strong beam tail was observed in inside of RF bucket 2. a weak, and wide-spread tail is observed in outside of RF bucket.

Page 53: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Recent investigation in coronagraph

Astronomers have a dream to observe planet system in outside of solar system.

They need contrast level of 10-10 !

Page 54: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Background in classical coronagraph

Re-diffraction intensity on the Lyot stop

Diffraction fringe exists here

This leakage of the light can make background level 10-8 (depends on Lyot stop condition).

Page 55: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Background level of 6x10-7 will good enough ?

no

YesUse classical coronagraph

Spatial coherence is good enough? Source like a point

no

No solution now

Null- interferometeric coronagraph

Page 56: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Null interferometeric coronagraphBackground level : about 10-10 (?)

Objective lens

Field lens

Baffle plate (Lyot stop)

Relay lens

Phase mask

Opaque disk

Classical coronagraph

Null interferometric coronagraph

Page 57: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Arrangement of null-interferometric coronagraph.

Astronomers say we can reach to the background level 10-10 !

Phase plate instead of opaque disk

Page 58: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

(II) OTR halo monitor for J-PARC

Page 59: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Optical design for OTR profile monitor in beam tranportline between 3.5GeV Rapid Cycle Synchrotron and 50GeV main ringThe beam size of proton beam is 5cm!2d observation of beam halo is alsoVery important!

Light source is OTR.

5cm

Page 60: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Beam halo

Beam core

screen with hole

OTR from beam haloBeam halo observation by screen with hole

Page 61: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Beam halo in far outside observed by fluorescent screens

Fluorescent screens

Page 62: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Fundamental design of OTR monitor

Page 63: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

RCS 3GeV

PS 12GeV

OTR intensity conpair with 12GeV proton synchrotron at KEK

Page 64: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Angular distribution of OTR from 3.5GeV Al foil target and proton beam

PS 12GeV

RCS 3GeV

Peak is in 350mrad!

Page 65: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Imaging device

few mrad

lens

OTR screen 45º

Large field depth by large object

Typical OTR profile monitor at electron machine

Page 66: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Imaging device

50 mrad

OTR screen 45º

Large field depth by large object

Toyoda, Mitsuhashi 2009 for slow extraction line at J-PARC

6000

mm

300mm

Page 67: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Large field depth by large object

500mrad

500m

m

45degree set up of target will impossible!Too long field depth!

Page 68: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

500m

rad

500mm

beam

Foil target must be normal to the beam!

Page 69: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Proton beamOffner relay system

Spherical 1st mirrorD=600mmR=500mm

Spherical 2ed mirrorD=200mmR=250mm

500 mrad

D=300mm 2枚

Page 70: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Design of Offner relay system

Object size: 50mm

General aperture 300mm

Page 71: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 72: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 73: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 74: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 75: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 76: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 77: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK
Page 78: Optical diagnostics for beam halo (I) Coronagraph (II) OTR halo monitor for J-PARC T. Mitsuhashi, KEK

Thank very much for your attention!