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CONSIDERATION OF BEAM INSTRUMENTATIONFOR SOLARIS LINAC UPGRADE
A. Curcio, INFN LNF, Frascati, Italy
R. Panaś, J. Biernat, M. Ünal, J. Wiechecki, A.I. Wawrzyniak∗ , NSRC SOLARIS, Kraków, Poland
Abstract
SOLARIS linac currently operates at 540 MeV and isused as an injector to the storage ring, where after the accumulation the energy is ramped up to 1.5 GeV via two active
RF cavities. Top-up injection would be of extreme benefits
for user operation, therefore a new 1.5 GeV linac is being
designed. The idea is to replace the current machine without
infrastructural interventions in terms of tunnel expansion.
Performed studies demonstrate that the best solution is provided by a Hybrid S-band/C-band LINAC. One of the main
goals is to achieve bunch compression below the picosecond
level and low-emittance beams for a future short-pulse facility or a Free Electron Laser. Within this presentation theresults of performed simulations will be presented together
with the concept of different diagnostics as BPMs, current
transformers, YAG screens, coherent diffraction radiation
monitor distribution.

INTRODUCTION
SOLARIS National Synchrotron Radiation Centre(NSRC) is first light source infrastructure built in Krakow,
Poland. Currently it consists of 600 MeV linac withthermionic gun, 1.5 GeV storage ring and 5 operating beamlines serving for the users community. The storage ring
operates in the decay mode with 2 injections during theday. An optimal perspective for the future operations at SOLARIS [1] would be the beam injection from the LINAC [2]into the storage ring at full energy, i.e. 1.5 GeV. There areseveral advantages related to this approach. The most intuitive is the possibility to keep the stored current at a constantlevel. This would favor the user operation requiring a constant level of brilliance of the synchrotron source and/orof the sources associated to insertion devices. The radiation source, therefore, can operate continuously, avoiding
injection downtime and energy ramp. Additionally, from an
operational point of view, all the machine settings, which arenormally current-depending, could be kept at the same value.
Avoiding invasive feedbacks meant to follow the electron
current’s decay, would allow the establishment of fine feedbacks working around equilibrium conditions for the beam
parameters (like emittance, optics and orbit stability). Fine
feedbacks could efficiently maintain optimal performances
for days.
Furthermore, having a 1.5 GeV LINAC machine would
open up a wide range of new possibilities for the facility,solely related to the LINAC as independent module. It’sworth specifying that in a top-up injection system the LINAC∗ adriana.wawrzyniak@uj.edu.plis permanently serving the storage ring, nevertheless a beamsplitter system might be thought in order to save a fractionof charge for diverse applications, bypassing the transfer line
to the ring. It has been already demonstrated the interest of
doing electron irradiations with the LINAC [3]. Currently, adiagnostic station placed before the LINAC dump is alreadyunder development for tests/experiments on novel conceptsof beam diagnostics [4]. A futuristic view of the same area
would foresee a Free Electron Laser (FEL). Indeed, such a
FEL source would be pulsed on a much shorter scale lengththan the pulses provided by the storage ring, and it would bedesigned to cover a different frequency range.

OPTICS DESIGN AND BEAM DYNAMICS
There were several considerations for the new linac design. However due to space constrains in the linac tunnel thedecision was made to change the technology from S-bandto C-band allowing for higher accelerating gradient. The
layout of the new LINAC placed in the existing tunnel isreported in Fig. 1. The schematics of the lattice elements
is, instead, reported in Fig. 5. Such schematics will be discussed later on in this paper, specifically regarding the beam
instrumentation used for beam diagnostics. The start-to-end
simulations studies, from the cathode to the injection point
for a Hybrid S-band/C-band LINAC were done by using theASTRA and elegant [5] codes. The start-to-end simulation
has been conducted for several different beam charges [6].
For the case of 100 pC the resulting beam optics in termsof rms beam sizes (Sigma 𝑥 and 𝑦) is reported in Fig. 2.
It is possible to notice that the beam size is maintained
within the range of a few hundreds microns all along theLINAC, corresponding to a normalized emittance 𝜀𝑁𝑥 ≃𝜀𝑁𝑦 ≲ 5 mm · mrad. The emittance at the gun is around
1 mm · mrad but it reaches such a value in the magnetic compressor due to space charge [6]. The final rms bunch length
𝑆𝑡 is in fact ≃500 fs rms, as depicted in Fig. 3. Such a shortbunch length may be used in the future to drive radiation
sources or to perform ultra-fast irradiations for different applications.

ERROR STUDIES
Once the start-to-end simulation studies have been finalized, spanning over beam parameters, and beam optics solutions have been found to efficiently transport low-emittance,
compressed beams, to the end of the full-energy LINAC,
investigation of the errors in the lattice elements has beenperformed. The goal has been to evaluate if the selectedfocusing elements and their positioning is suitable for preserving the beam optics even for non-ideal elements, andMOP008

01 Overview and Commissioning

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Figure 1: SOLARIS LINAC tunnel: gun on the left, transfer-line on the right.
Table 1: Rms value for the error distributions (all normal)
considered on different elements along the lattice.
Errors and units

Rms error value

Field Amplitude Error[MV/m]
Field Phase Error[deg]
Cavity/Quad/Solenoid Offset[mm]Cavity/Quad/Solenoid Rotation [mrad]
Solenoid Field Error[mT]
Quad Strength Error[1/m2 ]
Bending Radius Error
[m]

0.1
0.1
0.1
0.01
10.01
0.001

Figure 2: Evolution of the rms beam sizes (horizontal 𝑥 andvertical 𝑦) along the LINAC.

Figure 4: Error studies along linac.

Figure 3: Evolution of the bunch length along the LINAC.
as well to study the beam orbit and how (and where) tocorrect it in case of spurious offsets along the lattice. The
number of correctors has been set to 5 pairs: the first before
the magnetic chicane, the second after, two pairs along theC-band LINAC between sections, and finally a pair before
the transfer line. Concerning this latter, it includes an extra
horizontal corrector for the definition of the horizontal angle
of injection, as in the present layout of the SOLARIS injector
LINAC. The ”global” correction model for elements’ alignment has been assumed, in order to minimize the averageof error all along the machine, in both planes. For all theselected errors normal distributions have been considered,
where the rms error seeds are listed in Table 1. Errors havebeen considered both for magnetic and RF elements.

In Fig. 4 the beam centroids are shown with (solid lines)
and without (dashed lines) correction, when the errors presented in Table 1 are applied to the lattice configuration. A
global correction better than a few tens of microns is reachedin the 𝑥-plane and a correction on the level of a few microns
is reached for the vertical plane 𝑦. The difference is dueto the fact that the magnetic chicane disperse the beam in
the horizontal plane giving an extra kick to the beam to becompensated.

BEAM INSTRUMENTATIONThe electron beam diagnostics system should provide information required for the proper accelerator operation, as
well as ensure a safe operation. Several types of diagnostic tools to be used to measure the relevant quantities withsufficient precision.
The beam properties are planned to be measured at various places along the SOLARIS LINAC. The diagnostic
instruments that are foreseen for this purpose partially will
be reused from the existing machine. Currently, for beam

MOP0084601 Overview and Commissioning

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3Figure 5: New Elegant lattice including BPMs, correctors and screens.
position and feedback system the stripline BPMs with Libera single pass electronics and correction system is used.
For the linac upgarde the additional BPMs and correctors
need to be added. The transverse beam size and the beamemittance are within the set of most important parameters
for the beam characterisation. Therefore, emittance measurement stations will be available at several positions alongthe linac. The stations will be equipped with transverse
beam size monitors as YAG screens in the distance from thequadrupole magnets. The emittance will be measure with
the quadrupole scan. Moreover the YAG screens installedin the disperssive section of bunch compressor and transfer
line will allow to determine the energy spread of the bunch.
In Fig. 5 we show the latest version of the machine lattice,which includes BPMs, correctors and screens.
Table 2: Description table for the diagnostic flags depicted
in Fig. 5.
Flag

Diagnostics

123
4
5
67
8
9101112
13
14
15
16

BPM 1
Screen 1
Screen 2
BPM 2
Screen 3
BPM 3
BPM 4
BPM 5
Screen 4
BPM 6
Screen 5
Screen 6
BPM 7
BPM 8
BPM 9
Screen 7

In Table 2 we have listed the meaning of the 16 flags
found in the Elegant lattice at Fig. 5. The first two BPMs
are useful for the knowledge of the beam position at theentrance and exit of the magnetic compressor. The twoscreens in the compressor are used to measure the beamenergy spectrum, to check the alignment and the optics inthe magnetic chicane. The third screen is used for quadscan purposes, to measure the beam emittance. The BPMs
and screens along the C-band LINAC are used to check andcontrol the beam optics and orbit along the machine. The
fifth screen may be also used for quad scan purposes, with thecaveat of well-aligning the beam in the C-band that is placed
just before it (or switching it off during the measurement).

The last two BPMs can give information on the beam angle
at the injection.
The last screen yields the final beam profile, matched toenter transfer line. For the bunch length diagnostics sometests are undergoing based on the measurement of Coherent
Diffraction Radiation (CDR). Such a method provides information on a limited amount of spectral bands composing thebeam spectrum. Therefore, it strictly relies on a model or adirect measurement of the beam spectrum (bunch profile),in order to minimize the error of the measurement. Despite
several CDR diagnostic stations may be placed all along thenew machine to locally control the bunch length, a direct
diagnostic station for the bunch profile (and then spectrum
after Fourier transform) may be needed. The current idea isto introduce a S-band RF cavity at the end of the machine,on the straight line after the septum magnet which sends thebeam into the transfer line to the ring.
For the current measurement, current transformers will
be used distributed all along the machine. One of them may
be placed before the magnetic chicane, one after (to measure
the possible losses), then one in the middle of the lattice andone at the end after the last focusing doublet.

CONCLUSIONS
We have presented the most updated results for the beam
dynamics and the error studies on the newly designed SOLARIS injector LINAC. The Hybrid S-band/C-band technology presented allow for the 1.5 GeV energy LINAC design
within SOLARIS tunnel space constrains. This machine
will be necessary to implement the top-up injection at thesynchrotron facility. Specifically, we have presented the distribution of different beam instrumentation and diagnostics
all along the lattice configuration allowing for correctionof the beam trajectory with sub-micormeter level and fortransversal and longitudinal beam parameters measurements.

ACKNOWLEDGEMENTS
This project is executed under the provision of the Polish
Ministry and Higher Education project “Support for researchand development with the use of research infrastructure of
the National Synchrotron Radiation Centre SOLARIS” under contract nr 1/SOL/2021/2.

REFERENCES[1] A.I. Wawrzyniak, R. Panaś, A. Curcio, M. Knafel, G. Kowalski,
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IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - M O P 0 0 8

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

IBIC2023, Saskatoon, CanadaJACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
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MOP0084801 Overview and Commissioning