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GAS JET BASED FLUORESCENCE PROFILE MONITOR FOR LOW
ENERGY ELECTRONS AND HIGH ENERGY PROTONS AT LHC
O. Sedlacek∗1 , O. Stringer, C. Welsch, A. Webber-Date, H. Zhang
University of Liverpool and Cockcroft Institute, Daresbury, Warrington, UK
M. Ady, A. R. Churchman, S. Mazzoni, A. Rossi, M. Sameed, G. Schneider,
C. C. Sequeiro, K. Sidorowski, R. Veness, CERN, Geneva, Switzerland
P. Forck, S. Udrea, GSI, Darmstadt, Germany
1 also at CERN, Geneva, Switzerland
Abstract
The ever-developing accelerator capabilities of increasing
beam intensity, e.g. for High Luminosity LHC (HL-LHC),
demand novel non-invasive beam diagnostics. As a part of
the HL-LHC project a Beam Gas Curtain monitor (BGC), a
gas jet-based fluorescence transverse profile monitor, is being developed. The BGC uses a supersonic gas jet sheet thattraverses the beam at 45° and visualizes a two-dimensional
beam-induced fluorescent image. The principle of observing photons created by fluorescence makes the monitor insensitive to present electric or magnetic fields. Therefore,
the monitor is well suited for high-intensity beams such as
low-energy electron beam of Hollow Electron Lens (HEL),
and HL-LHC proton beam, either as a profile or an overlap
monitor. This talk will focus on the first gas jet measured
transverse profile of the 7 keV hollow electron beam. The
measurements were carried out at the Electron Beam Test
Stand at CERN testing up to 5 A beam for HEL. A comparison with Optical Transition Radiation measurements shows
consistency with the BGC results. The BGC installation ofJanuary 2023 at LHC is shown, including past results from
distributed gas fluorescence tests.

In this contribution, we report on the recent progress of
the BGC at the EBTS and present the configuration of theongoing LHC installation.

BGC INSTRUMENT
Principle of Detection
The BGC working principle is outlined in Fig. 1. The
monitor is based on a flat, supersonic gas jet referred to asa “curtain”, which perpendicularly crosses the beams’ pathwith the flat edge at 45° with respect to the horizontal plane(see Fig. 1). The beams excite the gas atoms or molecule
through collisions. Subsequent radiative deexcitation leads
to photon emission (fluorescence). The fluorescence footprint on the gas curtain thus directly relates to the particle
beams’ 2D transverse particle distributions, allowing forthe observation of the beams’ 2D transverse profiles in a
non-invasive way.

INTRODUCTION
The High Luminosity upgrade of the LHC (HL-LHC)
aims at extending its operability by a decade by increasing
its instantaneous luminosity by a factor of five beyond its
present design value [1]. The main feature of HL-LHC is
the upgrade of the focusing triplets to allow for a smaller𝛽∗ in the interaction region, combined with compact superconducting radio frequency crab cavities for bunch rotation.
For these systems to operate safely, a Hollow Electron Lens
(HEL) is being studied to improve the cleaning performanceof the collimation system. Optimal performance of the HEL
requires a means to measure the relative position of thehollow, low-energy electron beam with respect to the LHC
proton beam in a non-invasive way. It is in this context,
a collaboration between CERN, University of Liverpool
and GSI was established to design and produce a Beam Gas
Curtain (BGC) as an overlap monitor for the HEL [2–7]. The
strategy for commissioning the BGC consists of a parallel
validation of its performance in both the Electron Beam Test
Stand (EBTS) [8] and the LHC during the present run 3.
∗ Ondrej.Sedlacek@cern.ch

Figure 1: Working principle of the BGC.

Working Gas
Neon, nitrogen, and argon have been selected as working
gases for the BGC, each presenting advantages and disadvantages that affect the monitor’s performance. Their fluorescence processes are described in Eqs. (1) – (3):𝑁𝑒 + 𝑝/𝑒 − → (𝑁𝑒) ∗ + 𝑝/𝑒 − → 𝑁𝑒 + 𝛾 + 𝑝/𝑒 −(1)𝑁2 + 𝑝/𝑒 − → (𝑁2+ ) ∗ +𝑒 − + 𝑝/𝑒 − → 𝑁2+ +𝛾 +𝑒 − + 𝑝/𝑒 − (2)𝐴𝑟+𝑝/𝑒 − → ( 𝐴𝑟 + ) ∗ +𝑒 − +𝑝/𝑒 − → 𝐴𝑟 + +𝛾+𝑒 − +𝑝/𝑒 − (3)WE3I01312

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Neon gas curtains have the highest density. However, neonhas the lowest (expected) cross-sections and light yields. At
the same time, the relevant transition takes place within theneutral atom, see Eq. (1) at 585.4 nm [9, 10]. Therefore,
it is not affected by the beam’s space charge during theatom’s fluorescence lifetime1 of 16 ns. Additionally, neon
and argon are a noble gases and, as such, they don’t saturate
the Non-Evaporable Getter (NEG) coating often present at
LHC [10].
Nitrogen gas jets have the highest light yields. Its strongest
fluorescence line is expected at a wavelength of 391.4 nm.
It is a transition within the molecular ion N+2 with a lifetime1of 60 ns and, therefore, the beam’s space charge will interact
with the excited gas molecules and distort the observed distribution. The result of a simulation of the distortion caused by
one nominal LHC bunch is shown in Fig. 2. The distortion
increases the rms width of the observed distribution from350 µm to 490 µm. In the case of a bunch train the distortion reaches 570 µm. For more simulations of space-charge
distortions see [11].
Argon gas has two fluorescence peaks close to each otherat 454.5 nm and 476.5 nm. Using a wider optical filter to capture both peaks allows for a total light yield that is between nitrogen and neon at the expense of a higher background. The
transitions are ionic and therefore subject to space-charge
induced distortion but thanks to the short lifetime1 of 6 ns
and larger atomic mass compared to nitrogen the distortionis minimal.
For more information on the comparison of different working gasses using a Gaussian electron beam see [3].

temperature within the jet thus obtained. The third skimmer
is rectangular giving the jet its final curtain shape. The gas isin a molecular flow regime, allowing the jet to retain its rectangular cross-section throughout the path across the beam
pipe. After crossing the particle beams the jet is pumped
out in a dump chamber, which is separated from the interaction chamber by a fourth skimmer to limit back-scatteringof gas molecules and therefore minimise the pressure in theinteraction chamber.
Part of the photons created by fluorescence get focusedby a 40 mm dia., 160 mm focal length apochromatic lens
triplet onto a band-pass filter and are finally detected byan intensified camera. The optical band-pass filter limits
photons to the wavelengths of interest, e.g. 585 ± 10 nm
in the case of Ne. The intensified camera employs doublestage Micro Channel Plate (MCP) amplification allowing
for single photon detection.
The observed fluorescent light yield 𝑁 𝛾 is given by:
𝑁𝛾 = 𝑍 · 𝜎 ·Ω
𝐼 · Δ𝑡·𝑛·𝑑· 𝑇 · 𝑇 𝑓 · 𝜂pc · 𝜂MCP ,
𝑒
4𝜋

(4)

where 𝜎 is the fluorescence cross-section, 𝐼 the beam current,Δ𝑡 the integration time, 𝑍 the charge state of the passing
particle, 𝑒 the elementary charge, 𝑛 the curtain’s gas density,𝑑 the curtain’s effective thickness, Ω the acceptance solid
angle of the optical system, 𝑇 the transmittance of the opticalsystem including flange window, 𝑇 𝑓 the transmittance of the
optical filter, 𝜂pc the quantum efficiency of a photocathode,and 𝜂MCP the efficiency of a the MCP.

Profile Broadening Due to Curtain Thickness
The thickness of the gas jet curtain causes a broadeningof the observed vertical beam profile, since fluorescenceis produced in the whole volume of the curtain crossed by
the beam. Assuming rotational symmetry for the beam andcurtain homogeneity in the horizontal plane, the effect canbe modelled in 2D. In the case of the BGC the observed
profile 𝐼 (𝑦) is then [10]:∫ 𝑑/2
𝐼 (𝑦) =

Figure 2: Space charge effect on observed horizontal distribution of one nominal LHC bunch for a thin nitrogen curtain.

BGC Description
The supersonic gas curtain is created by letting the gas toexpand into vacuum through a small nozzle and (partly) propagate through a set of skimmers that ensure a low transverse
1 Average time between excitation and emission of relevant photon.

2
𝜌(𝜉)𝜙(𝑦 − √ 𝜉)𝑑𝜉,
−𝑑/2
2

(5)

where 𝜌 is the gas curtain density, 𝜙 the beam flux, 𝑑 thegas curtain thickness, 𝜉 the integration coordinate across thecurtain’s thickness, and 𝑦 the coordinate along the camera’s
detector, which in 2D is represented by a line.
Figure 3 shows simulations of profile broadening for a
Gaussian beam of rms width 𝜎beam due to a uniform gas curtain. For a curtain thickness 𝑑 = 𝜎beam and 𝑑 = 2 · 𝜎beam , theobserved 𝜎 is ≈ 1.08 · 𝜎beam and 1.37 · 𝜎beam , respectively.
In the case of the BGC at LHC, the skimmer thickness is
𝑑 = 2.7𝜎beam , causing a broadening of the vertical distribution of 61 %, as expected. This is acceptable due to thefact that the BGC was conceived as an overlap monitor for
the HEL at LHC, where the centroid rather than the profileof the transverse distribution is to be determined. In orderto accurately reconstruct the vertical profile, the thickness

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Figure 3: 2D estimations of a vertical beam profile broadening due to finite gas curtain thickness. The beam distribution
was chosen to be Gaussian with 𝜎 = 0.3 mm. The gas distribution was homogeneous within thickness 𝑑.

measurement errors. As mentioned earlier, the maximum
density is larger in the case of Ne, which is due to the difference in the number of degrees of freedom between Ne
atoms and N2 molecules.
Figure 5 plot c) shows the density profile of a nitrogencurtain obtained with a 0.7 mm thick 3rd skimmer. Using the smaller skimmer reduces the maximum density by≈25 % as well as its effective length down to 10.7 ± 0.7 nm.
This, combined with a reduced profile thickness, FWHM
of 11.7 ± 0.02 nm, will reduce the fluorescence light yield.
However, as experimentally observed at the EBTS, thesmaller skimmer leads to a lower background pressure of
8.63 · 10−8 mbar with respect to the one of 2.04 · 10−7 mbar
due to the larger one. This compensates the lower signal. In
addition, a lower thickness also reduces profile broadening,as pointed out in the previous section.

of the skimmer should be minimised and the broadening
accurately modelled for a realistic gas curtain profile.
For more detailed information see [10] and for simulationsof hollow beam profile broadening see [11].

GAS CURTAIN MEASUREMENTS
During the initial testing of the BGC in the lab at Cockcroft Institute, the interaction chamber was replaced witha special chamber containing a movable pressure gauge asshown in Fig. 4. An ion gauge is enclosed within a smallchamber with a 1 mm pinhole in the direction of the gas
jet. This experimental setup allows for gas density measurements within the portion of the gas jet that interacts with thebeam. For more details see [12, 13].

Figure 5: Gas curtain density measurements using a movablepressure gauge. Each pixel corresponds to a position of the
movable pressure gauge. a) N2 curtain using 0.7×9 mm 3rd
skimmer. b) Ne curtain using 0.7×9 mm 3rd skimmer. c) N2
curtain using 0.3×9 mm 3rd skimmer.

EXPERIMENTS WITH
HOLLOW ELECTRON BEAMS
Figure 4: Movable pressure gauge 3D model showing theenclosed ion gauge which is then attached to a stepper motor
for each direction. The gas density is sampled through a
1 mm pinhole [12].
The measured transverse density profiles of N2 and Ne
gas jets as obtained with a 0.7 mm thick 3rd skimmer are
shown in Fig. 5 plots a) and b), respectively. Both distributions exhibit a good density uniformity. The effective curtain
lengths are 12.5 ± 0.5 nm for N2 and 12.7 ± 0.6 nm for Ne.
There are no obvious differences between the shapes of thetwo profiles, both their lengths and thicknesses agree within

The EBTS currently serves as a test stand for the HEL.
The BGC was installed at the EBTS to validate its ability tomeasure a 7 keV hollow electron beam with up to 5 A peakcurrent. The electron beam is magnetized by immersion
in a magnetic field and then guided further in a solenoid
field. The outer and inner radius of the electron beam canbe varied by changing the magnetic field strengths.
Figure 6 shows BGC measurements of the hollow electron
beam’s transverse profile with different gases. The electron
beam was pulsed with a peak intensity of 1.5 A, a 25 µs
pulse duration and a 10 Hz repetition rate. Nitrogen, neon
and argon were used as working gases and the effective
integration time was equivalent to 2 s of a DC beam. The

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Figure 6: Beam gas curtain measurements of hollow electron
beam transverse profile. Nitrogen a), neon b), and argon c)were used as a working gas.
e-beam radii determined with each gas agree within themeasurement errors. As expected, the light yield of thenitrogen curtain was the highest, leading to the best image
quality. Neon curtains show the lowest light yield, while thehigher one of argon curtains is accompanied by a stronger
background. This is due to the wider bandwidth of the
optical filter used for Ar to allow for integration over several
spectral peaks.
The size of the beam was larger than that of the curtain,
therefore the distribution could be measured only partially.
This allowed for the measurement of the effective curtain size.
The 3rd skimmer used for this measurements was 0.3×9 mm
and the measured curtain effective length, 12.1 ± 0.3 nm,
was larger than expected from measurements with the movable pressure gauge shown in Fig. 5 c). However, it wasobserved that the exact width of the curtain slightly changes
from one alignment of the nozzle and skimmers to anotherwhich could explain the 1.4 mm difference.

place. Glassy carbon was the material of choice to sustain
the high charge density. The OTR signal was observed with asingle-stage intensified camera. Figure 7 shows a transverse
beam profile of a 7 keV, 1.1 A peak intensity pulsed hollow
electron beam, featuring 25 µs long pulses. The integration
time was equivalent to 2.5 ms of DC electron beam. The
observed distribution is rather smooth with a higher current
density towards the outer edge of the profile. The measured
beam size agrees with the BGC measurements. However,
due to a technical fault within one of the power supplies, themagnetic field around the electron gun was 25 % lower thanin the case of the EBTS measurements resulting in a smallertransverse profile. This might be explained a slight, but visible, ellipsoid shape of the observed distribution which might
be a measurement arte. For more OTR measurements ofhollow electron beams taken during another experimental
campaign see [14].

EXPERIMENTS WITH
LHC PROTON BEAMS
In 2022, BGC collaboration installed and operated an experiment at the LHC where Ne was injected in the beam pipe.
Figure 8 a) shows the installation. The preliminary results
and details of the installation were presented in Ref. [15].
In 2023, the gas jet was installed at the same position, completing the installation of the BGC at the LHC, as shown in
Fig. 8 b).

Figure 8: a) Distributed neon fluorescence experiment installation at LHC Point 4. b) Beam Gas curtain installation
at LHC Point 4.

Distributed Gas
Figure 7: Transverse profile of a 7 keV, 1.1 A peak intensity
hollow electron beam as measured with an OTR screen. The
profile was averaged over 100 beam pulses of 25 µs durationeach.
To benchmark the profiles measured by the BGC, an optical transition radiation (OTR) screen was installed in its

In the distributed gas experiment, a local pressure bumpof several meters in length was created in one of the LHC’s
beam pipes by injecting neon until a peak pressure of
2.2 · 10−8 mbar (Ne corrected) was reached. The fluorescence photons were captured by an optical system consisting of an apochromatic lens triplet, a band-pass filter at
585 ± 10 nm and a double-stage MCP intensified camera forsingle photon detection.

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Figure 9 shows a result from the fluorescence campaign.
This is a measurement of a full LHC beam with 1.5 · 1014
protons and an integration time of 430 s. The expected crosssection was estimated to be 4.7 · 10−22 cm2 in accordancewith [10].
Table 1: The optical system parameters of the BGC anddistributed gas experiment. The quantum efficiency of thephotocathode corresponds to the sensitivity around wavelengths of 585 nm. Units for optical acceptance are 4𝜋 Sr.
Parameter

Value

Optical acceptance
QE of PhotocathodeMCP efficiency
Transmittance of filter
Trans. of opt. system

1.43 · 10−3
0.09
0.75
0.80
0.85

Based on this expected cross-section and datasheet parameters of the optical system efficiencies, as summarisedin Table 1, the expected light yield was 2.5x higher thanobserved. This is rather good agreement with respect to thefact that only data points at very low energies were available
for the extrapolation of the expected cross-section. Several
sanity checks were performed to ensure the validity of thesignal. The signal rose with the integration time roughly
linearly. Turning off the gas injection caused the signal peakto vanish as expected. Lastly, varying the position of the
optical system distance along its optical axis did show thatthe beam is in focus.
The gas injection was validated also against increased
beam losses or any other effect on the beam. No visible additional losses above the noise were observed by the LHC operators, deeming the gas injection transparent for the beam.

deemed acceptable for a safe operation of the LHC. The
validation was done during beam injection, energy ramp
from 450 GeV to 6.8 TeV and finally collisions, i.e. for thewhole standard LHC fill.
The measured neon gas curtain density is equivalent toa pressure of 3.31 · 10−6 mbar at room temperature. This
constitutes an increase of the local gas density by a factorof 150.5. The smaller 0.3×9 mm 3rd skimmer was installed
to limit the gas load onto the LHC vacuum and improvethe background pressure. This choice, in comparison to thelarger 0.7×9 mm 3rd skimmer, reduces the gas jet thickness
by a factor of ≈2, and the curtain density by ≈25 %, but also
it’s broadening effect. The gas curtain installation allowed
for minimally invasive 2D distribution measurements witha significant integration time decrease. The first results are
currently being analysed.

CONCLUSIONSThis paper presents the BGC, a two-dimensional profile
monitor utilizing the fluorescence of a supersonic, curtain
shaped gas jet. The curtain density profile was measured forneon and nitrogen as well as for two sizes of the 3rd skimmer. The densities show good transverse uniformity. On the
EBTS, the transverse profile of the hollow electron beam
was measured using nitrogen, neon, and argon gas curtains.
The measured beam radii for each gas are in agreement. Furthermore, a hollow electron profile measurement using the
OTR method was shown. Fluorescence induced by 6.8 TeV
proton beam at LHC was measured during distributed gas
experiments. The results show a faint signal of the beam.
The BGC was installed at the LHC for two-dimensional
profile observations of the LHC beam. The first measurements show a significantly increased signal-to-noise ratio
compared to previous fluorescence experiments at the LHC.
The monitor was validated with the LHC beam and deemedsafe for LHC operation. The BGC is now in operation at the
LHC for characterisation with ultra-high energy proton andlead beams.

ACKNOWLEDGMENTS
Figure 9: Ne fluorescence measurements at LHC with distributed gas. a) Observed 2D distribution showing the LHC
beam horizontally across the field of view and a bright ringof synchrotron radiation. b) The horizontal profile of the
LHC beam [15].

BGC at LHC
At the beginning of 2023, the full BGC was installed at
the LHC, replacing the distributed gas injection with a neongas curtain injection and dump chamber.
Testing the gas curtain at LHC increased the backgroundpressure up to roughly 4 · 10−8 mbar. This is an acceptablelocal background pressure level for the LHC. The monitor operation with gas curtain injection was validated andThis work was supported by STFC under grant agreement
ST/P006752/1 and is a part of the HL-LHC project.

REFERENCES[1] A. Giorgio et al., “High luminosity large hadron collider HLLHC”, arXiv, 2017. doi:10.48550/arXiv.1705.08830[2] S. Udrea et al., “Development of a Fluorescence Based Gas
Sheet Profile Monitor for Use With Electron Lenses: Optical System Design and Preparatory Experiments”, in Proc.
IBIC’17, Grand Rapids, MI, USA, Aug. 2017, pp. 359–363.
doi:10.18429/JACoW-IBIC2017-WEPCC08[3] A. Salehilashkajani et al., “A gas curtain beam profile monitor
using beam induced fluorescence for high intensity charged
particle beams”, Appl. Phys. Lett., vol. 120, no. 17, 2022.
doi:10.1063/5.0085491

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03 Transverse Profile and Emittance Monitors

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - W E 3 I 0 1[4] A. Salehilashkajani et al., “Commissioning of the Prototype
for a New Gas Curtain Beam Profile Monitor Using Beam
Induced Fluorescence for HL-LHC”, in Proc. IPAC’19, Melbourne, Australia, May 2019, pp. 2709–2712.
doi:10.18429/JACoW-IPAC2019-WEPGW093[5] V. Tzoganis and C.P. Welsch, “A non-invasive beam profile
monitor for charged particle beams”, Appl. Phys. Lett., vol.
104, no. 20, p. 204104, 2014. doi:10.1063/1.4879285[6] H.D. Zhang et al., “A Supersonic Gas-Jet Based Beam Induced Fluorescence Prototype Monitor for Transverse Profile
Determination”, in Proc. IPAC’17, Copenhagen, Denmark,May 2017, pp. 458–461.
doi:10.18429/JACoW-IPAC2017-MOPAB139[7] H.D. Zhang et al., “A Supersonic Gas Jet-Based Beam Profile
Monitor Using Fluorescence for HL-LHC”, in Proc. IPAC’18,
Vancouver, Canada, Apr.-May 2018, pp. 1891–1894.
doi:10.18429/JACoW-IPAC2018-WEPAF034[10] S. Udrea and P. Forck, “Milestone1.1, 1.2, and 1.6 report”,
GSI, Darmstadt, Germany, 2018, Report No. CERN-EDMS2333411 and CERN-EDMS-2333413.
[11] O. Sedlacek et al., “Simulations of Space-Charge and Guiding
Fields Effects on the Performance of Gas Jet Profile Monitoring”, in Proc. IPAC’21, Campinas, Brazil, May 2021, pp. 898901. doi:10.18429/JACoW-IPAC2021-MOPAB283[12] H.D. Zhang, A. Salehilashkajani, O. Sedlacek, and C.P.
Welsch “Characterization of a supersonic gas jet for charged
particle beam profile monitor”, arXiv, 2022.
doi:10.48550/arXiv.2205.05386[13] H.D. Zhang et al., “Imaging a high-power hollow electron
beam non-invasively with a gas-jet-based beam profile monitor”, in Proc. IPAC’23, Venice, Italy, May 2023, pp. 45294532. doi:10.18429/JACoW-IPAC2023-THPL066[8] A. Rossi et al., “DC and Pulsed Electron Beam Test Facility at
CERN”, in Proc. IPAC’23, Venice, Italy, May 2023, pp. 1953–
1956. doi:10.18429/JACOW-IPAC2023-TUPL104[14] O. Sedlacek, M. Sameed, et al., “Optical Transition Radiation
Measurements of a High Intensity Low Energy Hollow Electron Beam on Electron Beam Test Facility”, in Proc. IPAC’23,
Venice, Italy, May 2023, pp. 3905-3908.
doi:10.18429/JACoW-IPAC2023-THPA002[9] R. Hampf, J. Wieser, and A. Ulrich, “Light emission processes in the context of optical beam profile monitors”, inEur. Phys. J., vol. 77, no. 51, 2023.
doi:10.1140/epjd/s10053-023-00624-6[15] O. Sedlacek et al., “HL-LHC Beam Gas Fluorescence Studies for Transverse Profile Measurement”, in Proc. IBIC’22,
Kraków, Poland, September 2022, pp. 261–264.
doi:10.18429/JACoW-IBIC2022-TUP17

WE3I0103 Transverse Profile and Emittance Monitors

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