Proceedings of IBIC2012, Tsukuba, Japan

WEIB01OVERVIEW OF ESS BEAM DIAGNOSTICS
A. Jansson, C. Böhme, B. Cheymol, H. Hassanzadegan, M. Jarosz, T. Shea, L. Tchelidze,
European Spallation Source ESS AB, Lund, Sweden
The European Spallation Source (ESS) will use a
2.5GeV superconducting proton linac with a 5MW
average beam power to produce the world’s mostpowerful neutron source. The project, sited in the south of
Sweden, is approaching the end of the pre-construction
phase, and is expected to enter the construction phase in
2013. This paper gives an overview of the ESS
accelerator and the planned beam diagnostics systems, aswell as the associated challenges.

THE ESS ACCELERATORThe European Spallation Source (ESS) is a 5MW linacbased neutron source, which will be built in Lund,
Sweden. It has a pulse repetition rate of 14Hz, a nominal
beam current of 50mA and a pulse length of
2.86ms.Acceleration is provided by a warm RFQ andDTL operating at 352MHz, followed by superconducting
spoke cavities (also at 352MHz), and two types of
elliptical cavities operating at 704MHz. The overall
length of the linac is about 400m, followed by andadditional 160m of upgrade space and transfer line.

beam stop. An inclined viewport to determine ion species
fraction by observing Doppler shifted luminescence lightis also foreseen.

IS

PLANNED DIAGNOSTICS SUITEThe ESS LINAC optics is under configuration control
since since 2010, with biannual updates. The discussion
below is based on the October 2012 lattice release. Thislattice is also the one that used in the Technical Design
Report.

Warm Linac
The LEBT (see Fig. 2) consists of two solenoids forfocussing (each equipped with a steering magnet) plus a
chopper to trim the beginning and end of the ion source
pulse. In the LEBT, the source emittance will bemeasured using a slit and one of two sets of SEM grids.
The SEM grids also allow measurement of the beamprofile and position directly. The beam current will bemeasured at the entry and exit using beam current
transformers. An insertable Faraday cup also allow for
beam current measurement and double as a temporary

Coll

Slit

FC

Grid

Sol

Grid BCM RFQ

Figure 2: LEBT diagnostics layout.
The MEBT[3] will have 10 quadrupoles, three buncher
cavities and a fast chopper (see Fig. 3). Here, thetransverse emittance from the RFQ will be measured witha slit and grid system, employing a slit design similar to
LINAC4. In addition, a set of 4 wire scanners will be used
to measure the beam profile. Two of these are co-locatedwith viewports for non-invasive profile measurement
based on luminescense, and two are co-located withtransverse halo measurement stations. Six BPMs will be
used for TOF and position measurement, and two BCT
will be inserted at the beginning and at the end of the line
for intensity and transmission measurement. A movable
Faraday cup allow for beam current measurement anddouble as a tune-up beam dump. Longitudinal beamprofile measurement will be performed with a Beam
Shape Monitor (BSM).

Figure 1: ESS linac layout overview.
The project is currently in a pre-construction phase. A
conceptual design report[1] was recently released, and a
Technical Design Report (TDR) along with an updated
cost estimate is planned for the beginning of 2013. An
overview of the current project status has been presented
in recent conference proceedings [2].

BCM SolStart of MEBTRFQ BCM BCM BPM

BPM

QH

QV

QH

NPM WSBPM

QV

BSM Coll Grid WS BCM BCM

QV

BPM

QH

QH

Halo WS

QV

Coll

Slit BPM

Halo NPM WS

QH

QV

BPM

FC

Figure 3: MEBT diagnostics layout.
The Drift Tube Linac (DTL) consists of four tanks (seeFig. 4). It employs a permanent magnet FODO latticeleaving empty drift tubes for diagnostics. The first tankwill have two BPMs, and the following tanks one BPM
each. The SNS-like inter-tank regions will each house awire scanner, a Faraday cup, and viewports for noninvasive profile monitoring. In addition, each tank will
have a BCT incorporated in the end wall.
BLM BLM BLM

BLM BLM BLM

TNK

TNK

BCM BPMBPM

NPM WSFC

BCM BPMBPM

BLM BLM BLM
TNK

BCM BPMNPM WSFC

BLM BLM BLM
TNK

BPM

NPM WSFC

BCM BPMBPM

BCM BCM Halo NPM WS

BSM

FC

Figure 4: DTL diagnostics layout.

ISBN 978-3-95450-119-9
Overview and Commissioning of Facilities1c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○AbstractMeasurement results for some typical time frames include: an average over one pulse, aa number of pulses, a sample within a pulse, an array of samples over a pulse, and fina
measurements surrounding the time of a trigger event (with the option of including pre trigg
WEIB01
Proceedings of IBIC2012, Tsukuba, Japanlast measurement type will provide the post-mortem data as required by the MPS. It wi
comprehensive data acquisition for machine studies and for diagnosis of subtle issues that do
Cold Linac and Upgrade Space
MPS trip. In addition to these measurement process variables, all systems will expose add
to allow
configuration, status monitoring, and debugging. All insertable devices (cThe cold linac consists of threevariables
main sections,using
providestatus
MPS such that only diagnostics beam is allowed when they are inserted
spoke cavities, medium beta ellipticalcavities
andtohighBLM,coldBCM,beta elliptical cavities, respectively.core.
The entire
linacand beam-on-target systems will provide MPS inputs so that beam ca
upon significant
uses a doublet lattice with one cryomodule
per cell inbeam
the loss, too much beam (for example, in the case of chopper failure),
Figuredump,
6: Target
properties at
andtransfer
target.line
Andiagnostics
option to layout.
interface the BPMs andspoke and medium beta section, andbeam
two cryomodules
perthe windows,
cell in the high beta section. There tois dedicatedforprovided.
MPS will space
also be
It is critical that the beam delivered to the target has thebeam diagnostics between the warm magnets in the right distribution. A local beam density that is too highdoublets. Here, it is foreseen to have one dual plane may lead to target damage. Therefore, a target beam
position pick-up attached to each magnet
three loss
4.8.2 andBeam
loss distribution monitoring system is needed. The same ismonitors placed before, between and after the true for the proton beam window, which separates theThebebeam
monitoring(BLM) vacuum
is arguably
diagnostic system ofquadrupoles. An additional BLM willplacedloss
betweenaccelerator
from thethe most
targetimportant
helium atmosphere.
It
has
the
dual
purposeofkeepingthemachinesafe
frombeam-induced
damage and avo
adjacent cryomodules in the high beta section. The layout Due to the importance of protecting the target, redundantmachineactivation
byprovidingcritical
input
to
the
machineprotection
system.
Thus, thof the spoke section is shown in Fig. 5.
methods are being pursued. A similar system will also be
be designed not to haveused
any
blind
spots.
In
addition,
as
the
BLM
systemwill
bea majorto monitor the model
beam sizeandon theresults
tune-up beam dump.
2 Simulation
tune-up, it should also be designed in a way that enables it to pin-point the loss location
possible.
“DAY ONE” DIAGNOSTICS
With this in mind, in the cold linac it is foreseen to have three ionization chambers (Some diagnostics system will mainly become importantsection, located before, between, and after the quads. The ICs will be placed as close as
when ramping up to production
power. However,certain (GeV/
Totalofenergy
deposition
beam pipe. Simulations show that this distribution
detectors should
allow to distinguishsystems need to function from “day one”, for initial
12of the quads from losses upstream4.151[?].
The
quads
are the locationsloss
whererate
the beam
size1
10include
protons/sec
andcommissioning.for
These
BLMs, BCMs, andBPMs.
therefore the most likelySome
loss locations.
In
the
warm
linac,
there
will
be
one
IC
per
DTL
ta
invasive “day one ” devices, such as Faraday Cups,
the inter-tank region) ascan
wellonlyas several
neutrondetectors(ND)
andscintillator
based
fast
be used with low power beam due to thermal
Figure 5: Spoke cavity section diagnostics layout. The
load.
other sections are similar.
BLM

BLM

BLM

BLM

BLM

BLM

BLM

BLM

BLM

BLM

BLM

BLM

FV

BPM

QV

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DV

BLM

BCM BPM
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WS

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BLM

BPM

QH

BLM

BLM

WS

NPM

BPM

QH

BSM

BPM

QH

BPM

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○

BPM

BPM

QH

CAVS

BPM

FC

QV

BPM BCM

BPM

Coll

Halo BPM

Grid PBW Img

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NPM Grid Halo

Img

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The cell length changes significantly between threemain sections, causing a change in the focussing. To
ensure proper matching, it is foreseen to equip the
beginning of each major section with four transverse
profile monitors and four longitudinal profile. Tungsten
wire scanners are the reference transverse profile devices.
They will be co-located with a system using a noninvasive technique, that can be used for full intensity. A
beam current monitor at the beginning of each section is
also foreseen.
The cold linac is followed by a 100m section of HEBT
which doubles as upgrade space[4]. It has the same
doublet optics as the high beta elliptical, but without
cryomodules. Consequently, instrumentation here issimilar to the high beta section.

Beam on Target and Dump

Towards the end of the HEBT there is a switchingmagnet that can send the beam either to the target (A2Tline) of the tune-up dump. The target spur has anachromatic vertical bend to go from the linac tunnel level
below grade to the target, which is above the ground
lossquadrupole
distributionmagnet,
from beamloss
on with 1 GeVlevel. Before the beam hits the target, it isFigure
expandedandLossFigure
4.151:
in the7:middle
first
in xz
plane,
Loss
inSimulated
theof middleof first
quadrupole
its distribution flattenend using octupoles. To verify the the aperture in the first doublet quadrupole in the highsection.
beam distribution and position in these magnets, each is beta magnet,
in xz plane, with 1 GeV
equipped with a wire scanner and a viewport for nonenergy.
invasive profile. Most quadrupoles are equipped with a Beam Loss
The beam loss monitoring (BLM) is arguably the most
BPM and a BLM for position and loss measurement (seeFig. 6). There is also a BCT to measure transmission and important diagnostic system of the ESS linac. It has thedual purpose of keeping the machine safe from beammonitor total beam on target.
induced damage and avoiding excessive machine
activation by providing critical input to the machine
protection system. Thus, the system must be designed forISBN 978-3-95450-119-9
2

Overview and Commissioning of Facilities

13

complete coverage of possible loss scenarios. In addition,
as the BLM system will be a major tool for beam tune-up,
it should also be designed in a way that enables it to pinpoint the loss location as precisely as possible. The
optimal location of detectors is being determined bysimulations (see Fig. 7).
Ionization chambers (ICs) will be the main beam loss
detector. SNS or CERN LHC type detectors may be used,
and are currently being evaluated. Fast PMT-based
detectors and neutron detectors will also be used in somelocations.
The required sensitivity for the ICs is set by the desire
to limit machine activation. The chosen criteria is that theBLM system should be able to detect a continuous loss
leading to beam pipe activation of 1% of the hands-on
maintenance limit (or about 0.01W/m). The response
time, on the other hand, is determined by the ability todetect large fast losses. Simulations show that if the entire
beam is lost in a single spot, it can melt steel in a matterof a few us in the warm linac (a few 10s of us in the cold
linac). Thus, the requirement for the BLMs system is todetect such a losses within 2us for the warm linac (10us
for the cold linac). SNS or LHC style ICs may be used,possibly with some modification.
At low energies, ionization chambers are not very
effective to detect beam loss due to the self shielding
from the RFQ and DTL tanks. Here differential current
measurement will be used as a complementary beam loss
detection mechanism.

WEIB01each quadrupole, since the goal of beam steering normallyis to center the beam in the quadrupoles. Again, the DTL
is the primary exception, since the permanent magnet
quadrupoles take most of the available space in a drift
tube, forcing the BPM to reside in its own drift tube. In
the A2T line, beam should be centered in the octupoles, so
BPMs will be located on or near these strong, non-linear
magnets. In the cold linac, BPMs can be installed in the
shadow of the quadrupole coils, requiring no extra
longitudinal space (see Fig. 8).
The BPM electronics will consist of a fast analog frontend, where the BPM signals will be received by sensitive
analog electronics, level adjusted and conditioned.
Following this, a digital section will digitize the signals
and processed them in an FPGA. Processing will benarrow band, and the processing frequency will bedifferent from the local cavity frequency (704MHz up to
the spoke section, and 352MHz from the elliptical cavity
sections onwards). Narrow band processing requires some
additional correction at the low energy end of the linac,
since the sensitivity for a given frequency is not only
given by the geometry of the pick-up, but also is afunction of the relativistic beta. The BPM electronics
should have a large enough dynamic range and a goodsignal-to-noise ratio so that they give useful results evenfor beam currents down to 5 mA and pulse lengths down
to 5 us respectively. A particular challenge is that during
tune up of the cold linac, beam may need to betransported very long distances to reach a beam dump,
and in the process the beam debunches, leading to asignificant drop in the harmonic content of the signal.

Emittance

Figure 8: Detail showing button BPM located in the
shadow of the quadrupole coil, requiring no extra
longitudinal space.

Beam Position
The BPM system will measure the beam position, thebeam phase with respect to the RF reference, as well as an
approximate beam current.
Button electrodes will be used, except in the DTL drift
tubes where special shorted striplines are foreseen. As far
as possible, BPM sensors will be physically attached to

Two emittance measurements will be permanently
installed in the warm linac and will be based on a slit andgrid system.
In the LEBT, preliminary estimations of the thermalload show that TZM, tungsten and graphite are well
suited for the slit material. Between the two solenoids, thebeam size is relatively large and the slit can handle thefull beam pulse.
Two SEM grids will be used to reconstruct the angular
distribution of the beam. Carbon wires are the primary
choice for the monitor due to the good thermal propertiesof this material, the grid pitch will has to determined infunction of the beam parameters. The complete
mechanical design is on going, and thermo mechanicalanalysis will provide the operating envelope of thesystem.
The MBT slit and grid system required a more
complicated design. At 3 MeV, the thermal load is an
issue and the slit cannot operate during the production
mode. Based on LINAC4 design [5], graphite is the bestsolution for slit material. To lower the thermal load, theenergy deposition is spread on a larger surface by tilting
the slit with respect to the beam axis. Figure 9 shows the
maximum temperature on the slit for 3 angles (45°, 30°
and 15°) in function of the beam pulse length.

ISBN 978-3-95450-119-9
Overview and Commissioning of Facilities3

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Proceedings of IBIC2012, Tsukuba, Japan

WEIB01

Proceedings of IBIC2012, Tsukuba, Japanc 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○used in production mode with external cooling. At low
energy, the secondary emission yield is large, and a bias
voltage is foreseen to suppress the secondary emission.
The challenge of the MEBT FC is to keep the thermalload below the mechanical limits of the FC, due to thesmall beam sizes and the large stopping power of 3 MeV
protons. This system will also feature a wide bandwidthchannel, capable of monitoring MEBT chopper
performance.
The design of the DTL Faraday cups is based on the
SNS design and includes an energy degrader in front of agraphite collector. The energy degrader absorbs the low
Figure 9: Maximum temperature on a graphite slit for energy particles that have fallen out of the accelerating
bucket. The thickness and the material of depends on the
different slit angle in function of the beam pulse length.
expected beam energy. The degrader also absorbs part of
The mechanical limits of graphite are around 1600 K, the beam that is at nominal energy, and the scattering will
the estimation of the temperature shows that the slit increase the beam sizes at the collector and reduce thecannot handle a 100 µs beam pulse. In order to preserve thermal load. The peak energy density is reduced by 10%
the slit integrity, the pulse length has to be reduced to 50 in case of graphite energy degrader and up to 30% with
µs, in this case, an angle of 30° is enough to keep the copper.
thermal load below the limits of the graphite.
Monte Carlo simulations show also that a nonThe other concern about the MEBT emittance meter is negligible amount of particles are created in the energy
the resolution of the profile monitor. Due to the short drift degrader. The amount of nuclear interaction increases
space, the pitch of the SEM grid shall be 100 µm for the with the beam energy and the particles produced canvertical plane and 300 µm for the horizontal plane in perturb the measurement. In the worst case, 3 % of the
M INSTRUMENTATION
133
order to reconstruct the beamlet profile with enough beam charge is lost in
the energy degrader, so that aaccuracy. These pitches cannot be achieved, other correction must be applied to the data in order to meet thesolution are considered like wire scanner or layer od accuracy requirements.
icated beam modes.
Exceptthe LEBT Faraday cup, the beam must be in the diagnostics
capton andmetal infoil.

Wire Scanners

BT Faraday Faraday
cup shall Cups
be installed in between the two solenoids, where
thescanners
beam sizes
are used only with a special shortWire
will beDuringthe commissioning
andthepowertuningdeposition
phase of thearge. Despite thelow energyof the beam,the
per unit
volumeishigh.
Thediagnostics pulse. In the warm linac section, the
ESSkeVlinac,
insertable
Faradayiscups
will 700
measurecurrent
n depth of a 75
protonin graphitearoundnm withthe maximum
the energy
calculationsofshowthat a carbon wire will survive if thewhile isolating
thetodownstream
accelerator
components
close to the surface.
In orderincrease power
handling,
graphite ofbeam
the shape
shown
in seepulse is reduced
to 100 us and 1 Hz repetition rate,
from
beam.
Duedesign
to thermalload,thetheLEBT
Faradaycups can5 will be used.
With
these
features,
Faradaycup is although
the onlythermionic
one capableofemissioncan be an issue.
only beinserted
into thepulse.
beam line
during dedicatedbeamshow Recent
ulses much longer
than
diagnostic
Preliminary
simulations
that thestudies
FC might
beperformed at GANIL show that carbon
Except incooling.
the LEBT Faraday cup, the beam must wires are incompatible with superconductive cavities, so
duction modemodes.
with externalbe in the diagnostics pulse mode.
tungsten wires are foreseen for wire scanners in the cold
linac. Due to the lower stopping power at high energy,
these wires will survive if they are used with a shortdiagnostic pulse.
At low energies, the secondary emission current on thewires will be used to determine the profile. Above 200
MeV, the profile will be reconstructed by sampling theshower created by the wire with a segmented scintillator;
the type and the geometry of the detector are still understudies. However, initial studies show that good linearity
can be obtained even in the short space available byFigure 10: LEBT graphite Faraday collector shape.
summing multiple detectors to avoid geometric effects
Figure 4.155: Graphite collector(see Fig. 11).
The LEBT Faraday cup will be installed in between theenergy, the secondary
emissionyield
is large,
and75 keV, large.
2 electrons are emitted for each
two solenoids,
where
the beamsizes
areatrelatively
Despitethe lowenergyandof thethe power
sing a boundary
betweenvacuumandbeam,a graphitefoil. deposition
A bias voltage is foreseen to suppress
ary emission. per unit volume is high due to the short penetration depth.
to increase
power
handling,cup
graphite
withinaorder to isolate this activity
ing and studyInof order
the RFQ
and MEBT,a Faraday
is foreseenbe usedchallenge(see Fig. 10).
WithFCthese
DTL and the special
rest ofshape
the will
linac.Theof thisis design
to keep the thermal load below
Faradaycup willbe andthe theonlylarge
one stopping power of 3 MeV
nical limits offeatures,
the FC,thedueLEBTto thesmall beamsizes
capableof handlingpulsesmuch longer
thancapable
diagnostic
his system will
also feature
a widebandwidthchannel,of monitoring MEBT chopper
pulse. Preliminary simulations show that the FC might bee.

ISBN 978-3-95450-119-9
4

Overview and Commissioning of Facilities

96
CHAPTER 4. ACCELERATOR

Proceedings of IBIC2012, Tsukuba, Japan

WEIB01Figure 11: Simulated energy depositon in four
scintillators placed around the beam pipe approximately
40cm downstream of a wire scanner, as a function of wire
position.

gure 4.163: Energy deposition on the 4 scintillators in function of the wire position (E=1GeV)MEASUREMENT CHALLENGES
Target Imaging
To monitor the power density on the target and proton
beam window, an imaging system similar to the one
developed at SNS is foreseen [6]. The baseline solution
employs luminescent coatings on beam-intercepting
surfaces. A dedicated instrumentation module within thetarget monolith (see Fig. 12) will contain optics to viewthe target face and the downstream side of the proton
beam window.

Figure13: Beam distribution on the proton beam window.
Figure 4.132: Particle density plots on the PBW and the target. Not(FigureofaAarhus
University)
beam courtesy
profiles onlinear scale.

Longitudinal Bunch Shapec 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○targetwillinnominally
exposedto a shortpeak currentof 52 µA/
Bunchesthe ESS be
LINAC
are very(see Figdensity
8),
by therefore
a maximum
currentof the84 µA/cm
in bothandoptions
to density
measurebunch 2 ,length
arecases scaled to2
As a reference,peak current
density of wide
250 µA/cm
would result fr
limited.
The lowa velocity
and relatively
aperture
flattening.
fixedbased
collimatorin current
the present
scenariomeanthat anyThedeviceon thewill
wall
or field
at intercept 8
the aperture have an intrinsic resolution much larger than
theLosses
bunchandlength.
Such a detector is based on measuring
apertures.
secondary electrons from a wire placed in the tail of theTails in the beam may lead to losses unless the apertures are suﬃciently
beam distribution. Since the process of electron emission
apertures drive the cost and have to be optimized. In Fig. 4.133 the tdoes not have a significant delay, very good time
both
together with the apertures in the magnets and vacuum ch
4.164: Maximum expected current on the wire in function of the beam energy in
SEM planes
mode
forresolution
canbeamin principle
be achieved.
Variants
such a correspondabsenceoflosses, whichwith thepresentofstatistics
wire (black line), tungsten wire (red line) and in shower mode (blue dots).
monitorwithoutaphysical
wire
have
been
developed
at front of the
Notice in particular the very large aperture needed in
GSI
and ANL,
and theseare interesting
options for
ESS.
observethe reduced
aperturesin the octupoles
as comparedto the q
Alastparticle
beam profile
section)
could
quadrupole
triplet scanner
will have(seeevennext
largerapertures
due to the expa
also be modified in order to measure the bunch length.
The
BSMs could also in principle be used as wire
Beam lines for tuning beam dumps.
scanners, but the baseline design separates these functions
initial setting-upof the
ESSforaccelerator,
and also during st
toDuring
allow optimizationof eachdevicetheir respective
beamline following the S1 line will transport the beam to a commiss
applications.

designed for 50 kW, and a quadrupole doublet will expand the beam
particular during the initial commissioning of the linac with many phwill impinge on the target with varying energies and energy spreads.
A diagnostic line will transport the beam to a second tuning beamwitha large ratio between dispersion and betafunction, and hence the
Figure 12: Target monolith schematic showing themeasured directly using profile monitors. Such measurements are othlocation of the target wheel, proton beam window and thealso include a quadrupole expansion of the beam to the planned 50 kW
diagnostics
with
opticalandfork,signalFigure 4.165:
Diagramplugof thewire
scannerthe paths.
beam is represented in red.
blocker) will be inserted in front of the dumps during maintenance per

The proton beam window presents a particulardevelopment challenge, since a thermal spray coating of
the type used at SNS would add significantly to thewindow’s mass. The proton beam window is also where
the beam density will be the highest (see Fig. 13). Due tothe importance of monitoring beam properties in thisregion, additional solutions are also being explored,
including gas fluorescence, wire grids, and opticaltransition radiation.

4.6.2

Collimation

Comprehensive simulations of the beam transport from the linac to thclearly some contingency has to be added in the present technical desig

Figure 14: Longitudinal beam distribution at the end of
the linac (Figure courtesy of R. Miyamoto, ESS).

ISBN 978-3-95450-119-9
Overview and Commissioning of Facilities5c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○WEIB01

Proceedings of IBIC2012, Tsukuba, Japan

Non-invasive Beam Profile

Halo

Since wire scanners can only be used for special low
power beams, non-invasive methods for measuring beamprofiles are being investigated in parallel. Some methods
in investigation are residual gas ionization (IPM) [7],luminescence (LPM) [8] and an electron scanning method[9]. These methods could allow measurements of thebeam profile during neutron production. However, they
are often not considered as exact as wire scanners andmay have limited resolution at low beam powers, so
invasive devices will be retained for cross calibrationeven where the non-invasive devices are installed.
Tests to establish the luminescence yield for vacuum
conditions similar to the ESS linac have been initiated incollaboration with SNS. A sketch of how such a monitor
could be integrated in the space available between doublet
quadrupoles is shown in Fig. 15.
The emitted light due to the interaction between the
beam and the residual gas can also be used to measure therelative fraction of ions species coming out of the ion
source. With a digital camera installed in the focal planeof a monochromator with a few tens of degree angle withrespect to the beam propagation axis, the Doppler shiftobservation of the Hα hydrogen Balmer series allows
isolating the fluorescence of each ions species of thebeam. The ratio of the different ions is proportional to thelight intensity [10].

In order to keep the losses at a small level, the beamtransverse halo will be measured at several locations
along the ESS linac and cleaned with several collimators.
In the warm linac, the halo measurement can be
performed with wire scanners equipped with high gain
and high dynamic range electronics. Similarly, the charge
deposition in the MEBT collimators can be alsomeasured. In the cold linac, this method cannot be
employed and different options are under investigation,such as the use of a wire scanner equipped with a
Cherenkov fiber, or the use of diamond detectors.
The radiation hardness of the material is an issue andthe life time of the detector remains to be estimated. The
drawback of these two methods is that they cannot
measure the profile of the beam core. In the UHB line, awire scanner equipped with a particle detector telescope
will be used in counting mode to measure beam core andhalo with the same device.
Within the target monolith, thermocouples surrounding
the physical aperture will be used to measure position of
the beam envelope.

SUMMARY
This paper has outlined diagnostics suite for the ESS
accelerator, and some particular challenges related to it.
An overview of the various types of instruments indifferent parts of the LINAC is given in Table 1.

REFERENCES

Figure 15: Sketch showing possible integration of ashower mode wire scanner (scintillator shown in green)with a dual plane luminescence monitor and pumpout port
between doublet magnets in the High Beta upgrade
section.

[1] ESS Conceptual Design Report[2] H. Danared et al, Design of the ESS Accelerator,
IPAC12, New Orleans, LA[3] I. Bustinduy, Medium Energy Beam Transport
Design Update For ESS, IPAC12, New Orleans, LA[4] A I Sander-Holm et al, The Layout of the HighEnergy Beam Transport for the European Spallation
Source, IPAC12, New Orleans[5] B. Cheymol et al., “Design of the Emittance Meter
for the 3 and 12 MeV LINAC4 H- Beam”, IPAC’10,
Kyoto, Japan[6] T.J. Shea et al., "Installation and initial operation of
an on-line target imaging system for SNS",
Proceedings of 19th meeting on International
Collaboration of Advanced Neutron Sources (ICANSXIX), Grindelwald, Switzerland, PSI-Proceedings
10-01 / ISSN-Nr. 1019-6447, March 2010.
[7] C. Böhme et al, TUPB12, DIPAC09[8] C. Böhme et al, TUPB10, DIPAC09[9] W. Blokland et al, TUOA03, DIPAC09[10] F. Senee et al., “Diagnostics for High Power Ions
Beams with Coherent Optic Fiber for IFMIF-EVEDA
Injector”, DIPAC’ 09, Basel, Switzerland

ISBN 978-3-95450-119-9
6

Overview and Commissioning of Facilities

Proceedings of IBIC2012, Tsukuba, Japan

WEIB01

Section

BL
M

BCM

BPM

Slit
(H+V)

Grids

2

2

1

4

4

1

1

28

5

5

3

3

MEBT

4

6

6

8

1

2

1

1

1

1

4

4

Opticalimaging

BSM

2

WS

NonInvasive

Halo

LEBT

(H+V
)

FC

Profile

DTL

12

Spoke

42

Low Beta
Elliptical

48

2

32

4

4

4

4

High Beta
Elliptical

60

1

30

4

4

4

4

HEBT (toswitch)

22

2

14

4

4

2

2

Target
Line

20

2

16

2

3

3

2

4

Dump
Line

10

2

8

1

1

1

1

1

Total

214

21

142

29

28

3

21

2

5

6

15

ISBN 978-3-95450-119-9
Overview and Commissioning of Facilities

7

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Table 1: Summary of Planned Instrumentation Systems