SYNCHROTRON LIGHT MONITOR FOR THE ADVANCED
PHOTON SOURCE BOOSTER SYNCHROTRON
WEP015K. P. Wootton, W. J. Berg, W. P. Burns III, J. R. Calvey, J. C. Dooling, L. Erwin, A. H. Lumpkin, N. S. Sereno, S. Shoaf, S. G. Wang
Argonne National Laboratory, Lemont, IL, USA

ABSTRACTMOTIVATION▪ A new synchrotron light monitor
has been tested for the booster
synchrotron of the Advanced
Photon Source.
▪ Visible light synchrotron radiationis collected by a mirror anddirected to an optical imagingsystem and camera.
▪ In the present work, we describe
the present synchrotron radiation
diagnostic layout.
▪ An analysis of the synchrotron
radiation power on the mirror, theoptical layout with components,and features of the control system
will be presented.

▪ Synchrotron radiation (SR) presents asignificant thermal load on components
in electron storage rings.
▪ The motivation for the present work is
to enable accurate measurement ofbeam properties during high-charge
studies of the booster synchrotron for
the Advanced Photon Source Upgrade(APS-U) [1,2].
▪ During those studies, it appears that themirror that reflects SR out of thevacuum (or its support) deflects underthermal load from SR [3].

SR POWER ON THE MIRROR▪ Beam profile monitors are required to support beam size
measurements of the electron beam in the booster.
▪ Three photon ports are available for use as synchrotron light
photon monitors in the booster [4-7].
▪ Previously, only two ports had been instrumented, and underthermal loading, the mirrors in these ports deform so much thatthe image of the beam is deflected off sensors used to measure
the beam transverse and longitudinal dimensions [3].
▪ Routine measurements of electron beam such as emittance andenergy spread are difficult.
▪ We propose to instrument all three photon monitors. The positionof the beam image on the beam profile monitors needs to remain
within a small enough displacement from nominal that it does not
move off laterally the imaging and diagnostic devices.

BEAMLINE LATTICE

NEW PROFILE MONITOR▪ For an electron beam, the vertical distribution of SR powerd𝑃
is [8]:dΩ2𝜓2d𝑃
15𝛾= 5.42𝐸 4 𝐵𝐼𝑏1+,
22225/2dΩ
7 1+𝛾 𝜓1+𝛾 𝜓▪

BACKGROUNDd𝑃
The peak power density (on-axis)
in units of W mrad-2dΩ

is given by [8]:d𝑃
= 5.42 𝐸 4 𝐵𝐼𝑏 ,dΩ▪ Integrating over the vertical angle, the power density in thed𝑃
horizontal directionin units of W mrad-1 is given by [8]:dΩd𝑃
= 4.22 𝐸 3 𝐵𝐼𝑏dΩ

▪ The beam profile monitor optical path andprincipal components are illustrated
schematically in Fig. 4.
▪ Components of the beam profile monitor are
located physically within the booster
synchrotron enclosure, which is illustrated inFig. 5.

▪ Small average SR beam power on the mirror (4.1 W),endeavoured to improve imaging stability using a rigid
mirror assembly composed of a bulk material.
▪ Glidcop was selected as the mirror substrate material.
▪ Mirror was fabricated and polished in-house. The mirror
substrate was cut and then polished using Loose Abrasive
Polishing (lapping) to achieve the desired mirror surface
finish. The mirror surface was specified as 60-40 scratchdig, and a flatness error of 1𝜆. The mirror geometry isillustrated in Fig. 6.
For polishing, lapping wasperformed in several stages.
Glidcop Mirror and polishing
fixture assembly were mounted
in a precision vice on an
Okamoto surface grinder (Fig.
7). The finished polished mirror
is illustrated in Fig. 8.
Fig. 6: Mirror geometry.

Fig. 1: Energy with time.

Fig. 4: Schematic of beamprofile monitor in thebooster ring. (a) SR fromelectron beam. (b) Glidcop
mirror. (c) Out-of-vacuum
mirror. (d) Motorised zoomfocus lens. (e) Digital
camera.

Fig. 2: SR power with energy.
Table 1: Booster and Electron
Beam Parameters
ParameterFig. 3: SR power with time.
Integrate with duty factor 0.25,4.1 W.

ChargeBeam current
SR source to mirror
Bending radius
Energy at injection
Energy at extraction
Ramp time (E_i-E_e)
Booster period
Photon port width
Photon port height

SymbolValue𝑞𝐼𝑏𝑑𝜌
𝐸𝑖𝐸𝑒𝑡𝑟𝑇𝐵𝑤ℎ

17 nC
13.9 mA
2.85 m33.3 m425 MeV
7.1 GeV0.25 s
1.0 s
60 mm
37 mm

Fig. 7: Photograph of the mirror
and polishing fixture duringmachine lapping.

IMAGE STABILITYSUMMARY▪ We have tested the mirror
performance in machinestudies.
▪ Most demanding test was 5 nC
beam charge at 2 Hz repetition
rate. Average 2.4 W SR poweron the mirror (compared to thedesign of 4.1 W).
▪ Observed beam using twomonitors: existing (B:SLM1)
and new (B:SLM3).
▪ The motion of the beam image
on both monitors is illustrated inFig. 9.

Fig. 5: Photograph of beamprofile monitor in the booster
ring.

Fig. 9: Image centroid with time.

▪ Specified, designed and fabricated a mirror toobserve and image visible synchrotron lightfrom the booster synchrotron at the APS.
▪ Calculated the SR power on mirror under
anticipated beam conditions for APS-U
operations (4.1 W).
▪ Mirror was fabricated and installed.
▪ Tested mirror under representative loading.
Mirror achieves the primary objective of stable
SR transport without measurable distortion.

Fig. 8: Finished mirror after finalpolishing.

REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

J. R. Calvey et al., “Simulations of Booster Injection Efficiency for the APS-Upgrade,” in Proc.
NAPAC’16, Chicago, IL, USA, Oct. 2016, pp. 647–650.
doi:10.18429/JACoW-NAPAC2016-WEA1CO03
K.C. Harkay et al., “High-Charge Injector for on-Axis Injection Into A High-Performance Storage Ring
Light Source,” in Proc. IPAC’19, Melbourne, Australia, May 2019, pp. 3423–3426.
doi:10.18429/JACoW-IPAC2019-THYYPLM3
J. C. Dooling et al., “Measurements of Bunch Length in the Advanced Photon Source Booster
Synchrotron”, in Proc. NAPAC’22, Albuquerque, NM, USA, Aug. 2022, pp. 394–397.
doi:10.18429/JACoW-NAPAC2022-TUPA22
B. Yang, A.H. Lumpkin, “The Planned Photon Diagnostics Beamlines at the Advanced PhotonSource”, AIP Conf. Proc., vol. 333, no. 1, pp. 252–258, May 1995. doi:10.1063/1.48048
B.X. Yang, A.H. Lumpkin, M. Borland, K. Harkay, and A. Nassiri, “Characterization of Beam
Dynamics in the APS Injector Rings Using Time-Resolved Imaging Techniques”, in Proc. PAC’97,
Vancouver, Canada, May 1997, paper 5P040, pp. 2052–2054. doi:10.1109/PAC.1997.751104
A. Lumpkin and B. Yang, “Status of the Synchrotron Radiation Monitors for the APS Facility Rings”,in Proc. PAC’95, Dallas, TX, USA, May 1995, paper MPQ09, pp. 2470–2472.
doi:10.1109/PAC.1995.505587
A. Lumpkin et al., “Initial Diagnostics Commissioning Results for the Advanced Photon Source(APS)”, in Proc. PAC’95, Dallas, TX, USA, May 1995, paper MPQ10, pp. 2473–2475.
doi:10.1109/PAC.1995.505588
R.P. Walker, “Synchrotron radiation”, in CAS - CERN Accelerator School: 5th General Accelerator
Physics Course (7-18 Sep. 1992, Jyväskylä, Finland), Technical Report CERN-94-01, pp. 437-459,
1994. doi:10.5170/CERN-1994-001.437

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