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

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UPGRADE OF THE ELBE TIMING SYSTEM
M. Kuntzsch, A. Schwarz, K. Zenker, M. Justus
Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Z. Oven, L. Perusko, L. Krmpotic, U. Legat, U. Rojec, Cosylab, Ljubljana, Slovenia
Abstract
The ELBE center for high power radiation sources is operating an electron linear accelerator to generate various
secondary radiation like neutrons, positrons, intense THz
and IR pulses and Bremsstrahlung. The legacy timing system has been modified and extend over the past two decades to enable new experiments. Part of this system is using obsolete parts which makes the maintenance more
complex and the heterogenous structure requires a majorrevision of the timing signal generation and distribution atELBE.
A new timing system based on the Micro Research Finland hardware platform is being adapted to be used atELBE. It will enable parallel operation of two electron
sources and subsequent kickers to serve multiple end stations at a time. The hardware enables low jitter emission oftiming patterns and a long term drift compensation of thedistribution network. In spring 2023 the development of
the software has been accomplished, which included themapping of operation modes and different complex beam
patterns onto the capabilities of the commercial MRF platform. The system generates complex beam patterns fromsingle pulse, to macro pulse and 26 MHz continuous wave
(CW) operation, including special triggers for diagnostics
and machine subsystems.

REQUIREMENTS
The requirements for the new timing system have been
derived mainly from the features of the old timing systemand feature requests from the ELBE user community. Timing signal receivers as well as operators expect a particularcomposition of different signals, that have to be deliveredby the new timing system.
Even though ELBE is a CW machine, a macro pulser isused to generate pulsed, low current beams. This mode ismainly used for beam tuning in order to allow a safe operation of destructive diagnostics like view screens. The
macro pulser setting defines in turn also the timing for diagnostic triggers for the low level radio frequency (LLRF)
controllers, cameras and loss monitors. If in operation, themacro pulser chops the beam into short bursts using magnetic steerer coils. The inductance of the coils combinedwith the capabilities of the driver unit define the rising andfalling slope of the macro pulse train. At ELBE slew rates
are on the 10 µs scale and define the shortest opening timeof 100 µs. The minimal period is derived from the maximum camera sampling time of 10 ms. So, the period canbe set to multiples of 10 ms up to many minutes period.
Biological experiments at ELBE require a very complex
trigger pattern in order to adjust the applied dose and its
structure to a sample with high accuracy. At the same time

the background radiation needs to be reduced which meansto suppress dark current from the injector section.
For this application a dedicated single pulser systemneeds to be in place, which allows for patterns with single
bunch resolution, periods up to minutes and a possibility to
combine the gun pulse emission with a macro pulse gate tosuppress dark current. These features are required for both
thermionic injector and superconducting radiofrequency(SRF) gun that are available at ELBE.
Table 1 summarizes the main pulser modes of the timing
system and their parameter range. In detail, the requirements are much more complex, the edge cases and error
handling makes the implementation a complex development. The complete specification has been written into adesign documents which serves as a reference for the implementation process.
Table 1: Main Pulser Modes and Their Parameter Ranges
UnitMinMax
Electron Bunch Rate
Hz
0.03
26e6
Macro Pulser Periods
10e-333864
Macro Pulser Duty Cycles
100e-633864
Single Pulser Periods115.5e-9 33864
Single Pulser Durations
38.5e-9 33864

SYSTEM DESCRIPTION
Hardware
For the implementation at ELBE different systems havebeen evaluated and after a comprehensive feasibility study
a European Tender has been awarded to COSYLAB to set
up the new ELBE timing system. As hardware platform theMicro Research Finland Oy (MRF) timing modules havebeen selected [1].
The latest revision of the MRF hardware is available forMicroTCA standard, which is becoming more and more
popular in accelerator community and found its application
for new beam diagnostic systems and LLRF systems atELBE.
The system consists of event master modules (EVM)
that are generating and send a continuous stream of events
which are received by event receiver modules (EVR).
EVRs are located in different sections around the accelerator and generate physical trigger signals based on theevent stream. EVMs and EVRs are connected over opticalfibers, forming a hierarchic structure which allows for ahigh flexibility and the possibility to extend the systemwith ease.
Each EVR has four fixed TTL outputs on the front paneland provides two slots for universal IO modules, eachhousing two physical outputs. There are universal IO modules for different logic levels, electrical and optical outputs

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and special outputs that allow for a fine delay with picosecond precision. Standard modules can delay output signals with the precision of an event clock cycle. In addition
a dedicated rear transition module can be attached to theEVR, providing five additional slots for universal IO modules. A fully equipped EVR can in turn deliver 18 output
signals to connected timing clients. Timing clients in thesame MicroTCA crate can be triggered through the differential backplane trigger bus.
The interconnections between EVMs and EVRs are subject to timing drifts due to changing environmental conditions. The system offers an active drift stabilization, minimizing the residual instability to < 10 ps peak-peak.
The event clock rate can be selected from 50 MHz to166.6 MHz, and has been defined to 130 MHz at ELBE.
This is a ten times the nominal ELBE bunch repetition rateof 13 MHz and one tenth of the accelerator cavity frequency of 1.3 GHz. This event clock rate defines the minimum spacing between to events to 7.7 ns.
At ELBE one EVM is set up per injector, allowing forindependent operation in separate beamlines and combined
emission into the ELBE accelerator. For machine timing
receivers like beam diagnostics LLRF MicroTCA EVRs
are applied. For users that do not use MicroTCA hardware
we provide PCIe based receiver modules, which is morecost effective.

Software
While the hardware could be used from stock, the Software needed to be tailored to the requirements of ELBE.
The base implementation is done using EPICS and EPICS
mrfioc2 module [2]. This offers access to all features of thetiming system, diagnostic functionality and basic graphicaluser interfaces (GUI).
The logical mapping of the ELBE machine structure tosoftware is a complex process. It reflects the operation of
two injectors in parallel, different beamline sections andbeam modes. The above-mentioned beam modes, macropulse, single pulse and CW are realized as sequences ofevents, combined with prescalers in order to generatebunch triggers, triggers for LLRF, macro pulser, kicker anddiagnostics. The sequences are being built by a algorithm,
that translates the user defined parameters into the correct
EVM and EVR settings. This complex algorithm, the handling of edge cases and error handling is the major effort
needed for the system integration.
The graphical user interfaces are designed using Phoebus [3]. In the course of the design process it has been extended and offers now a simple way to control the operation modes of the timing system, parameter checks, error
handling and status information of all hardware components (Fig. 1).
The Phoebus Interface is mainly used for system test andcommissioning. Currently a interface for the ELBESCADA system WinCC is developed which will make thetiming system a part of the operator panels used for the machine control.

Figure 1: ELBE Timing System Phoebus GUIs to control
injectors, EVR outputs and a status panel of all EVMs andEVRs
All machine parameters are checked by a master programmable logic controller (PLC) which acts as the main
instance for machine protection. User commands and status signals from the timing system are processed and interlock signals are generated accordingly.

WORK IN PROGRESSIn spring 2023 the development of the software has beenaccomplished, which included the mapping of operation
mode and different complex beam patterns onto the capabilities of the commercial platform. Figure 2 shows thesetup used for the intensive on-site software tests.
In parallel, machine development shifts have been used
to test all components at the ELBE accelerator. Especiallythe machine protection system functionality and parametertransfer between timing hardware and MPS PLC has beentested thoroughly to ensure safe operation of the system.
In a next step the complete transition from the legacy
system to the new timing system will be made. While allold timing system generators will be replaced by MRF
hardware in one step, the old timing distribution system
can be replaced stepwise. The whole process means a major change to the operation of the ELBE accelerator andneeds to be planned in great detail in order to ensure aseamless transition und not to lose time devoted to user operation.

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

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3IBIC2023, 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 - W E P 0 4 3

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

CONCLUSION
A new flexible timing system has been developed for theELBE accelerator. The system will replace many hardware
components which are generating timing signals for ELBE
and unify the timing pattern generation as well as the distribution in one modular system.
The software development has been finalized in spring
2023, dedicated machine development shifts have beenused to implement and test the interface to the machine
protection.
In a final step the legacy hardware will be replaced by
MRF components and the new timing system will be theonly source of clock signals for the ELBE operation.

REFERENCES[1] Micro Research Finlad Oy, http://www.mrf.fi[2] EPICS mrfioc2,
https://github.com/epics-modules/mrfioc2/[3] SNS Controls CS-Studio,

https://controlssoftware.sns.ornl.gov/css_phoebus/

Figure 2: Timing System Test Setup.

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