BEAMLINE FOR TIME DOMAIN PHOTON DIAGNOSTICS AT
THE ADVANCED PHOTON SOURCE UPGRADE
WEP016K. P. Wootton, W. Cheng, G. Decker, N. S. Sereno, F. Westferro
Argonne National Laboratory, Lemont, IL, USAABSTRACT▪ Time domain photon diagnostics
are proposed for electron beamcharacterisation and operation of
the Advanced Photon Source
Upgrade storage ring.
▪ In the present work, we present
updated status on the timedomain X-ray and visible photon
diagnostic beamline for theAdvanced Photon Source
Upgrade.
▪ We outline design influencesleading to the proposed beamline
layout, in particular long-term
maintenance and commonality
with other beamlines at theAdvanced Photon Source.

DESIGN INFLUENCES

MOTIVATION▪ The Advanced Photon Source Upgrade (APSU) project is presently underway, with the goalof increasing the brilliance of photon beams touser beamlines at the Advanced Photon
Source (APS) [1-3].
▪ A number of user programs take advantage ofthe fill pattern for time-resolved X-ray
techniques.
▪ As these user programs are anticipated tocontinue during APS-U operations, we areproviding temporal photon beam diagnostics
for the optimisation and diagnostics ofaccelerator operations.
▪ In the present work, we present updated
status on the time-domain X-ray and visible
photon diagnostic beamline at 35-BM for theAPS-U. We outline design influences leading
to the proposed beamline layout, in particularlong-term maintenance and commonality withother beamlines at the APS.

FRONT END

▪ The beamline layout has matured through the design process, with subtle
but notable changes since our previous work on this beamline [4]. In
particular, we have made a concerted effort to utilise components
standardised across APS-U bending magnet front ends and beamlines to
the greatest extent possible.
▪ For the APS, the 35-BM front-end and beamline employed a geometry
optimised for providing multiple independent photon beams for diagnostics[5,6]. The beamline featured three branch lines (X-ray, visible, X-ray)
separated horizontally in angle from the bending magnet source. Thevisible light beamline passed a large vertical angular acceptance of± 2.9 mrad (Fig. 1). Several practical constraints steered us away fromadopting the existing 35-BM geometry directly for APS-U.
▪ It is envisaged that two diagnostic beamlines will be operated for routine
beam diagnostics measurements for APS-U. Transverse beam sizes andemittances will be observed using the 38-AM bending magnet beamline [710]. Bunch length and bunch purity will be observed using visible light and
X-ray diagnostics at the 35-BM beamline [4]. To meet the long-term needfor time-domain diagnostics at 35-BM, a large vertical aperture is notstrictly required for either the X-ray or visible light photon diagnostics.
Hence rather than creating large vertical opening apertures in many
components of the 35-BM front end, we instead start our design from thenew bending magnet front end (BMFE) for user APS-U bending magnet
beamlines [2]. The opening angle of visible synchrotron radiation andbeamline apertures are illustrated in Fig. 2.
▪ The choice to start from the standard user BMFE design affords us
opportunities to standardise many beamline components and control
equipment. We anticipate that this will be beneficial for long-term
maintenance of the beamline.

▪

The beamline layout on a standard APS sector is illustrated in Fig. 6. From the perspective of the X-ray
beamline, the most significant change between the APS and APS-U machine is the lateral offset of 42mm inboard of the new X-ray source point [2]. As a result, the new beamline centerline is 42 mm
inboard of the previous beamline. Fortuitously, 35-BM features a unique shielded X-ray transportpassing through the 35-BM-B hutch. The beam transport is actually two separate beam transporttubes, separated horizontally. As a result, we are able to configure the beamline to employ the inboard
beam transport with minimal changes to the beamline components. Beamline components areillustrated in profile view in Fig. 7.

X-Ray Path
▪ Figure 3 shows the scope of thechanges to the front end for 35-BM.
The standard BMFE is designed topass X-rays through the thebeamline (and protect the beamline
when shutters are closed), so nochanges to the standard BMFE areneeded to accommodate X-ray beamtransport to the shielded enclosuresof 35-BM.
Visible Light Path
▪ For visible light, two essentialchanges are needed to the first fixedmask (FM1) and the visible lightmirror. The vertical aperture of FM1
was increased by modifying acompleted FM1 assembly using wirecut electrical discharge machining.
This increases the opening angle ofsynchrotron radiation accepted by
the beamline to ~ ± 0.35 mrad. The
enlarged machined aperture of FM1
is illustrated in Fig. 4.
▪ A mirror inclined at 45° was used toreflect visible synchrotron radiation
upwards. For APS [Fig. 3(b)], thismirror was at 𝑧 ≈ 15 m, while for
APS-U [Fig. 3(a)], we position thenew mirror at 𝑧 ≈ 19.8 m. Thislocation was selected because it
replaces the second X-ray BeamPosition Monitor (XBPM2) in thestandard BFME [2]. A water-cooled
and vertically translatable stage for
XBPM2 provide the required control
for this optical mirror. The visible lightmirror is shown installed in its
vacuum chamber in Fig. 5.
▪ Thermal analysis of the visible lightmirror was performed using finite
element analysis. For routine
beamline operations, we intend forthe mirror to sit below the orbit planeof the ring, intercepting the lower fanof visible light synchrotron radiation
in a manner similar to Refs. [11,12].
Using the translatable vertical stage,
the mirror can be moved completely
into the beam path to intercept visible
light above and below the orbit planeof the ring, however this isanticipated to be used only for
dedicated machine studies with very
low stored beam current.
▪ Beyond the first mirror, visible lightwill be transported in air by reflecting
the light using planar mirrors to theoptical enclosure 35-BM-B. The
optical transport is enclosed bystainless steel tubing.

▪ The principal long-term purpose of the X-ray beamline
configuration is to preserve X-ray beam transport from the35-BM-A through to 35-BM-C hutches, for use with thebunch purity monitor diagnostic [13,14].
▪ However the beamline can also be used as configured for
an X-ray pinhole camera for beam size measurements.
Four blades of white-beam slits (z=24 m) can be closed toform a rectangular pinhole aperture.
▪ A scintillator and optical microscope can be positioned
near the end of the beamline (z=45 m) in order to image
the electron beam in the APS-U storage ring with an X-raypinhole magnification 21/24=0.875. Parameters of theelectron beam and pinhole camera in the horizontal plane
are summarised in Table 1.

Fig. 3: Comparison of 35-BM front ends forAPS-U and APS. The horizontal axis z is thedistance from the bending magnet source inmetres. (a) Front end configuration for APS-U.
(i) First Fixed Mask. (ii) Visible Light Mirror.
(b) Front end configuration for APS.

Fig. 4: Machining of FM1 vertical aperture
to increase the vertical aperture for visible
light propagation. The narrower slot (atright) is used to pass X-rays through to the
X-ray beamline enclosures. The beam
direction in this figure is into the page.

Table 1: Pinhole Camera Parameters.
Parameter
Beta function
Emittance
Energy spread
Dispersion
Beam size (source)
Pinhole magnification
Beam size (scintillator)

Symbol

Value

𝛽𝑥
𝜀𝑥
𝛿
𝜂𝑥
𝜎𝑥
𝑀
Σ𝑥

0.84 m42 pm rad0.156%
3.67 mm
8.3 µm
0.875
7.2 µm▪ We anticipate that the spatial resolution needed to image
an X-ray spot size of Gaussian distribution Σ𝑥 = 6.2 μm is
challenging, but not beyond technical feasibility. We
anticipate that few-μm resolution may be achievable byusing a 20 μm thick single-crystal scintillator such as
Cerium-doped Yttrium Aluminium Garnet imaged by an
optical microscope with numerical aperture between 0.4–
1.0 [15].
Fig. 6: Illustration of 35-BM beamline layout for APS-U
operations. The horizontal axis z is the distance from thebending magnet source in metres. The beam direction inthis figure is from top to bottom.

Fig. 7: Illustration of 35-BM beamline profile for APS-U
operations. The horizontal axis z is the distance from the bending
magnet source in metres. The beam direction in this figure is from
top to bottom.

SUMMARY▪ In the present work, we have presented updated
status on the time-domain X-ray and visible photon
diagnostic beamline for the Advanced Photon
Source Upgrade.

Fig. 5: Visible light mirror. The beam
direction in this figure is into thepage.

Fig. 2: Vertical profile of bending magnet synchrotron radiation
accepted by 35-BM for APS-U storage ring. The vacuum chamber
wall blocks synchrotron radiation at angles ±1.0 mrad. The first fixedmask (FM1) blocks synchrotron radiation at angles > ±0.35 mrad.

OUTLOOKBEAMLINE▪ 35-BM has been operational as adiagnostic beamline at APS for many
years [5,6]. We summarise featuresof the front end and beamline layout
for APS-U. The beamline front end
for APS-U and APS is illustrated inFig. 3.

Fig. 1: Vertical profile of bending magnet synchrotron radiation
accepted by 35-BM for APS storage ring. The cold finger masks
synchrotron radiation over the central ±0.5 mrad.

▪ We have outlined design influences leading to theproposed beamline layout, in particular long-term
maintenance and commonality with otherbeamlines at the Advanced Photon Source.
▪ Beyond its primary use as a time-domain
diagnostic, we additionally outline potential use of
the beamline to image the electron beam
distribution in the horizontal plane.

REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]

T. E. Fornek, “Advanced Photon Source Upgrade Project Final Design Report”, Argonne National Laboratory, Lemont, IL, USA, Rep.
APSU-2.01-RPT-003, May 2019. doi:10.2172/1543138
T. E. Fornek, “Advanced Photon Source Upgrade Project Preliminary Design Report”, Argonne National Laboratory, Lemont, IL, USA,Rep. APSU-2.01-RPT-002, Sep. 2017. doi:10.2172/1423830
M. Borland et al., “The Upgrade of the Advanced Photon Source”, in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver,Canada, Apr.-May 2018, pp. 2872–2877. doi:10.18429/JACoW-IPAC2018-THXGBD1
K. P. Wootton et al., “Time Domain Photon Diagnostics for the Advanced Photon Source Upgrade”, in Proc. IBIC’21, Pohang, Korea,Sep. 2021, pp. 356–360. doi:10.18429/JACoW-IBIC2021-WEPP02
B. Yang and A. H. Lumpkin, “The Planned Photon Diagnostics Beamlines at the Advanced Photon Source”, AIP Conf. Proc., vol. 333,
pp. 252–258 (1995). doi:10.1063/1.48048
A. Lumpkin, and B. Yang, “Status of the synchrotron radiation monitors for the APS facility rings”, in Proc. 16 th Particle Accelerator
Conf. (PAC’95), Dallas, TX, USA, May 1995, paper MPQ09, pp. 2470–2472. doi:10.1109/PAC.1995.505587
B. X. Yang et al., “High-Energy X-Ray Pinhole Camera for High-Resolution Electron Beam Size Measurements”, in Proc. IBIC’16,Barcelona, Spain, Sep. 2016, pp. 504–507. doi:10.18429/JACoW-IBIC2016-TUPG66
B. X. Yang and S. H. Lee, “Planned x-ray diffraction diagnostics for APS Upgrade emittance measurements”, presented at TopicalWorkshop on Emittance Measurements for Light Sources and FELs, Barcelona, Spain, Jan. 2018, unpublished.
K. P. Wootton, W. X. Cheng, G. Decker, S. H. Lee, and B. X. Yang, “X-Ray Beam Size Monitor Enclosure for the Advanced Photon
Source Upgrade”, in Proc. IBIC’20, Santos, Brazil, Sep. 2020, pp. 34–36. doi:10.18429/JACoW-IBIC2020-TUPP05K. P. Wootton et al., “Design of the X-Ray Beam Size Monitor for the Advanced Photon Source Upgrade”, in Proc. IPAC’21, Campinas,Brazil, May 2021, pp. 956–959. doi:10.18429/JACoW-IPAC2021-MOPAB303
J. C. Bergstrom, J. M. Vogt, “The optical diagnostic beamline at the Canadian Light Source”, Nucl. Instrum. Methods Phys. Res., Sect.
A, vol. 562, pp. 495–512, Jun. 2006. doi:10.1016/j.nima.2006.02.200
M. J. Boland et al., “X-ray and Optical Diagnostic Beamlines at the Australian Synchrotron Storage Ring”, in Proc. EPAC’06,Edinburgh, UK, Jun. 2006, paper THPLS002, pp. 3263–3265.
W. E. Norum and B. X. Yang, “A Novel FPGA-Based Bunch Purity Monitor System at the APS Storage Ring”, in Proc. 22nd Particle
Accelerator Conf. (PAC’07), Albuquerque, NM, USA, Jun. 2007, paper FRPMN115, pp. 4384–4386.
doi:10.1109/PAC.2007.4440014
B. X. Yang, W. E. Norum, S. E. Shoaf, and J. B. Stevens, “Bunch-by-Bunch Diagnostics at the APS Using Time-Correlated
Single-Photon Counting Techniques”, in Proc. 14th Beam Instrumentation Workshop (BIW’10), Santa Fe, NM, USA, May 2010, paper
TUPSM044, pp. 238–242.
T. Martin, A. Koch, “Recent developments in X-ray imaging with micrometer spatial resolution”, J. Synchrotron Radiat., vol. 13, pp.
180–194, Jan. 2006. doi:10.1107/S0909049506000550

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”).
Argonne, a U.S. Department of Energy Office of Science Laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S.
Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article toreproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of theGovernment. The Department of Energy will provide public access to these results of federally sponsored research in accordancewith the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan