Study of Visible Synchrotron Radiation Monitor on SOLEIL
Booster
IBIC 2023
A. Moutardier ∗ , G.Cauchon, M. Chevrot, Z. Fan, N. Hubert, S. Kubsky, M. Labat, M. Thomasset, Synchrotron SOLEIL, Gif-Sur-Yvette, France∗

alexandre.moutardier@synchrotron-soleil.fr

Abstract
In the scope of SOLEIL II, the booster must also be upgraded to reduce from 130 to 5 nm.rad the emittance of the beam delivered to the ring. Control of the emittance in the booster will become crucial to ensure thenominal performance of the storage ring injection. The SOLEIL I booster is already equipped with a Visible Synchrotron Radiation Monitor (MRSV). This equipment, made of an extraction mirror and a simple opticalsystem, was originally planned to be used only for beam presence verification but has not been used routinely for operation since the commissioning in 2005. The control and acquisition systems had to be refreshed to beusable again and allow the beam size measurement along the booster energy ramp. The extraction mirror was replaced due to unexpected degradation leading to a second spot appearing on the camera. This paper traces
back the MRSV upgrades from understanding the cause of mirror degradation until mirror replacement and the first proper beam visualisation, achieved at the beginning of 2023.

MRSV theory
MRSV : Visible Synchrotron Radiation Monitor
MRSV design

Point-Spread-Function (PSF)

Measurei.e. light emission by an unique electron

11.132 mSilver mirror

1.0405 m

Photon

UHV window
Lens 1
Lens 2
Square slit

Electron

dipoleDensity
Lens 3

CameraFigure 1: MRSV design.

Double spot issue

Figure 2: Image of synchrotron radiation taken during commissioning of a new mirror.

Beam profile at the end of the booster ramp coherent with simulations.

Figure 3: SRW [3] simulations of synchrotron radiation for a) one electron (PSF), b) a beam.

Image spot size = convolution of real electron beam
size and PSF

Mirror study• 2005 : SOLEIL commissioning

Thermal study• 2006 : Second spot on MRSV images :Damaged mirror← Iridescence = Heat damage← Black strip = carbon deposition
For mirror surface study, the carFigure 6:
Booster’s bon deposition was removed using
MRSV extraction mirror, a O2 plasma chamber [4].

Figure 4: MRSV image 18 years after the SOLEIL
commissioning.

after nearly 18 years ofoperation.

On the mirror :Mirror surface study• 2023: extraction mirror replace ⇒ Fig. 2

Figure 7: Ansys [6] thermal
simulation of Pyrex mirror (a)and copper one (b), both silver
coated.

• Total average power : 6 W• 4 µm deep valley• 2 weeks after: Image already distorted• Average power density :0.26 W mm−2

• Melt silver down valley• Mirror deformation :Angle between upperand lower half of the Figure 8: Interferometry [5]of MRSV extraction mirror surmirror

face. (a) 3D map, (b) line cut
Black strip + mirror deforma- along top image.
Figure 5: MRSV image 2 weeks after mirror exchange.

tion ⇒ 2 spots on imagesConclusion• Double spot issue comes from mirror degradation• Those degradations are due to overheating because of poor heat transfers of Pyrex glass• A copper-based mirror is installed to increase heat transfers and hopefully prevent mirrordegradation• MRSV can be used to measure electron beam size, hence beam emittance• This work is useful for the SOLEIL booster upgrade and associated diagnostics design.

Mirrorheat transfer(W m−1 K−1 )Max heat
Withoutcoating

(a)

(b)

1.2

400496°

197°

1000°

-References[1]
acA1920-50gm
Baslerace
GigE
camera,https://docs.baslerweb.com/aca1920-50gm[2] Å. Andersson and al., Determination of a small vertical electron
beam profile and emittance at the Swiss Light Source, NIM A 591 (3),437 - 446 (2008).
[3] O. Chubar and P. Elleaume, Accurate and efficient computation of synchrotron radiation in the near field region, Proceedingsof EPAC’98, Stockholm, Sweden, 1998, 88.
[4] DIENER Pico Diener Plasma GmbH & Co. KG, Ebhausen, Germany.
[5] firebolt, (GBS) mbH, Ilmenau, Germany[6] Ansys® Academic Research Mechanical, Release 2020R2, 2020.

Acknowledgements
S. Morand, M.-A. Tordeux (SOLEIL).