Coronagraph for beam halo observation for the HL LHC And X-ray interferometer for the measurement of extremely small apparent beam size in FCC-ee

1. Coronagraph for the observation of beam halo at HL LHC

1-1. What is the coronagraph? an introduction

Diffraction pattern (with interference fringe) taken by sCMOS low noise and high dynamic range camera at ASLS

Diffraction fringes Gaussian beam profile Convolution between diffraction fringes and beam profile

Diffraction fringes Gaussian beam profile Convolution between diffraction fringes and beam profile Blocked by opaque disk

Optical system of Lyot’s corona graph Objective lens Field lens Baffle plate (Lyot stop) Relay lens Opaque disk Many of idea such as baffle plates, light trap material, anti-reflection disk etc. are applied to reduce background scattering light.

3 stages-optical system in the Lyot’s coronagraph 1st stage : Objective lens system 2ed stage : re-diffraction system 3ed stage : Relay lens

Observation in PF, KEK 2005 Beam core (superimposed) + halo Observation with better than 6 order of magnitude

Beam tail images in the single bunch operation at the KEK PF measured at different current Multi-bunch bunch current 1.42mA

Observation for the more out side Single bunch 65.8mA Exposure 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 Far tail Observation for the more out side

1-2. Plan of halo observation by using the coronagraph in HL LHC Phase1: Test observation (2016- ), Designed and constructing a coronagraph by modifying the coronagraph constructed in 2005 in the KEK. Aiming a halo observation with 103 to 104 contrast to the beam core, and it will set in B2 SR monitor line. Phase2: Design and construct an optimum coronagraph for the LHC, aiming 105 to 106 contrast.

1-3. Key conditions for design the coronagraph for LHC (2015). LHC(B2) Distance between source point and objective lens 28.5m Beam size in horizontal (1s of beam core) 330mm/3.75mmrad 270mm/2.5mmrad Beam size in vertical 430mm/3.75mmrad 350mm/2.5mmrad Minimum size of opaque disk against beam core 5 s of beam core

The optical design of phase 1 coronagraph LHC(B2) Focal length of objective lens 2000mm Objective lens aperture 25 x 25 mm Transverse magnification 0.0754 Opaque disk size 0.2-2mm Focal length of field lens 816mm Movable range of Lyot stop 2 x 2mm to 20 x 20 mm Focal length of relay lens and Magnifier lens 500mm 12.5-25mm

1-4. Diffraction in Coronagraph

Opaque disk Objective lens

Re-diffraction optical system Opaque disk Re-diffraction optics system Field lens Objective system Re-diffraction optical system Function of the field lens : make a image of objective lens aperture onto Lyot stop

Diffraction in re-diffraction system

Lyot stop at +/-5mm

Re-diffraction optical system Opaque disk Lyot stop Re-diffraction optics system Objective lens Re-diffraction optical system Blocking diffraction fringe by

Lyot stop Field lens Blocking diffraction fringe by

Lyot stop at +/-5mm

Diffraction background at 3ed stage in log scale 3.7x10-4

Background from diffraction is depending to leakage of diffraction fringes in inside of Lyot stop

1-5. Mie-scattering noise from optical component surface

Background source in coronagraph Noise from defects on the Objective lens surface (inside) such as scratches and digs. 2. Noise from the optical components (mirrors) in front of the coronagraph. 3. Reflections in inside wall. 4. Noise from dust in air. 5. Rayleigh scattering from air molecule. 6. Turbulence of the air

Background source in coronagraph 1.Noise from defects on the Objective lens surface (inside) such as scratches and digs. 2. Noise from the optical components (mirrors) in front of the coronagraph. 3. Reflections in inside wall. Apply baffles and anti-reflection materials 4. Noise from dust in air. Apply dust filter 5. Rayleigh scattering from air molecule. Not significant in few meter optical path 6. Turbulence of air Not significant in few meter optical path

Digs on glass surface of scratch & dig 60/40 The optical surface quality 60/40 guarantees no larger scratches than 6mm width, and no larger dig than 400mm. 5mm 200mm

Simulation result of background produced by dig on objective surface

Example of Mie-Scattering noise

How to eliminate Mie scattering?? A careful optical polishing for the objective lens. Reduce number of glass surface. use a singlet lens for the objective lens. 3. No coating (Anti-reflection, Neutral density etc.) for objective lens.

Comparison between normal optical polish and careful optical polish for coronagraph S&D 60/40 surface of the lens Surface of the coronagraph lens

1-5. Optical testing of Phase 1 coronagraph with 30m optical testing line

30m Optical testing line for Phase 1 coronagraph

Light source

Phase 1 coronagraph set on one end of optical line

Diffraction without Lyot stop Exposure time 200msec

Elimination of diffraction with Lyot stop Exposure time 500msec

2x10-7 to the peak intensity 425mm Exposure time 10sec 1x10-4 to the peak intensity

Artificial halo source, plastic plate with some finger prints.

425mm 500msec Artificial halo

Summary for expected performance for phase 1 coronagraph The diffraction background in phase1 coronagraph is estimated to 3.7x10-4 (experimentally 1 x 10-4 ). Except 2 fringes in the centre, most of diffraction fringes have intensities of 10-5 to 10-6 range. From Optical testing, Mie-scattering noise from the extraction mirror seems negligible.

2. X-ray interferometer for the measurement of extremely small apparent beam size in FCC-ee

2-1. Parameters of FCC-ee at source point Bending magnet length 24.585m Bending radius 11590.8m Magnetic field strength 0.0503T Bending angle 2.144mrad Beam energy and current 175GeV 6.6mA 45GeV 1500mA emittance 1.3pmrad Estimated vertical beam size sy =5.1mm / b=20m =0.05mrad / 100m

2-2. Expected spectrum from the bending magnet FCC-ee 45GeV 175GeV Brightness (photons / mrad2 1%bandwidth) Frequency integrated power 6.5W/ mrad for 175GeV 5.6W/mrad for 45GeV Photon energy (keV)

175GeV r=11590.8m 0.1nm Divergence of beam Order of 10-7rad Divergence of SR Order of 10-5rad q in rad

2-3. Extraction of hard X-rays from the ring Light source: last bending magnet in Arc. 45-50mm Estimated vacuum duct in the straight section after the last bending magnet

Bending radius 11590.8m 24.858m 2.144mrad 1.072mrad 100m 107.2mm Geometrical condition for the extraction of SR from the last bending magnet Enough separation between orbit and extraction structure of the vacuum duct is necessary to escape from corrective effect. Some similar structure such as crotch absorber and branch optical beam line seems necessary to protect the crotch of the vacuum chamber from strong irradiation of SR. 50m 53.6mm Source point: center of the magnet

Apparent size of object Long distance Short distance Observation point

Angular diameter Angular diameter is given by, q=a/d or qs=s/d a q d Object locates having a size a at certain distance d Angular diameter is given by, q=a/d or qs=s/d

wavelength Visible light imaging 500nm 50 500 5000 X-ray pinhole 0.1nm method wavelength measurable minimum beme size in angular diameter in mrad Corresponding size in 100m in mm Corresponding size in 1000m in mm Visible light imaging 500nm 50 500 5000 X-ray pinhole 0.1nm 0. 5 FZP imaging Of soft X-ray 0.35nm 0.3 30 300 Visible light interferometry 400nm 0.47 47 470 Interferometry with imbalance input 0.2 (scaled) No measurement 20 200 Coded aperture 0.3nm 0.5 0.1 (estimation) 10 100 X-ray (new method) 0.01 1 10mm

2-4. Simple double slit X-ray interferometer (Young type) Double slit D=20-few100mm, a=8mm K-edge filter Be-window

We do not need selection of polarization q in rad 175GeV r=11590.8m Double slit location We do not need selection of polarization Iv / Ih =0.016

Double slit of interferometer will not miss the beam size information Divergence of SR Order of 10-5rad Divergence of beam Order of 10-7rad Double slit of interferometer will not miss the beam size information

Spatial coherence vs. beam size D=300mm, f=100m g Beam size (mm) l=0.1nm

Expected interferogram for g=0.65 (beam size of 5mm at 100m) Double slit a=5um, D=300um f=100m Monochromatic l=0.1nm

Krypton gas filter has a nice window around 10keV

With quasi-monochromatic ray Kr gas filter 100mm Dl/l=20% Dl/l=50%

Double slit interferometer (Young type) with total reflection mirror Double slit D=20-100mm, a=8mm K-edge filter Be-window 1.0-1.5deg Totally reflection mirror Length of 1m g-ray

Background subtraction Interference fringe which is observed by the simple Young type double slit interferometer has no reference baseline

we can identify the background as an background with no input light. We can crosscheck this issue with observing a single slit diffraction pattern by hiding one slit of double slit

Summery for FCC e-e X-ray interferometer has a good resolution for 5mm beam size in FCC e-e with distance of 100m. 2. The system seems very simple, and easy to construction. 3. A similar system such as crotch absorber etc. are necessary to safety extraction of X-rays. 4. Mechanical vibration issue is very important due to shorter wavelength. Carful design of mechanical structure is necessary.

Thank you for your attention

Instantaneous diffraction pattern at focus point of Objective lens is given by, Apparent diffraction pattern on focus point is given by integrating instantaneous diffraction pattern in incoherent manner ,

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

How is the performance of coronagraph limited? 1-6. Phase 2 coronagraph How is the performance of coronagraph limited?

Corse period correspond to inner aperture diameter Fine period correspond to outer aperture diameter

Back to diffraction fringe on Lyot　stop 0.162mm 0.6mm 1.0mm

Back to diffraction fringe on Lyot　stop 0.162mm 0.6mm 1.0mm Larger opaque disk has small diffraction fringe

Phase 2 coronagraph 1. The leakage of diffraction fringe reduces by increase of opaque disk diameter. We can realize better contrast with larger transverse magnification. We should design the focal length of objective lens longer. 2. Chromatic shift on optical axis is given by focal length divided by the Abbe number, designing long focal length increases drastically increase the chromatic foal shift. We should apply reflector focusing system for the objective instead of the objective lens system in phase 2.

16000mm 8000mm 4000mm 5000mm Coronagraph having a magnification of 0.5 (about 7 times larger transverse magnification) Objective lens Opaque disk Lyot stop Field lens relay lens

Reduction the actual length of long focus of the simple objective lens with a combination of focus and defocus lenses. Telephoto type lens

Telephoto type with reflectors First mirror concave Second mirror convex Focus of first mirror Synthesized focus of two mirrors

Optical design Entrance pupil for the first stage Objective mirror system f=8000mm Magnification ≈0.5 First mirror concave R=4000mm Second mirror convex R= -800mm Entrance pupil for re-diffraction system Field lens Lyot stop 8mm x 8mm Relay lens Magnification =1 5000mm 5200mm 1700mm

Diffraction background at 3ed stage In Log scale 2x10-6 to 10-7

Expected performance of Phase 2 coronagraph The diffraction background in phase1 coronagraph is estimated to 2x10-6 to 10-7 . Gaussian appodization at relay lens aperture can improve the contrast of noise diffraction down to 10-9. Such appodization increase width of diffraction for halo image, and will reduce spatial resolution.