ARCHIVE SYSTEM FOR INJECTION CURRENT AT SuperKEKB
H. Kaji∗ A) , Y. IitsukaB) , M. HiroseC)
A)
KEK, Ibaraki, JapanB)
East Japan Institute of Technology Co., Ltd., Ibaraki, JapanC)
Kanto Information Service Co., Ltd., Ibaraki, Japan
Abstract
The archive system for the injection information is developed for the SuperKEKB collider. The information isarchived in pulse by pulse so that the detailed studies ofinjection condition become possible. It is necessary to keephigh efficiency of injection. The system consists of databaseserver and the module of Event Timing System. The fluctuation and significant loss of injected current are observed.
The archive is implemented in the entire phase-2 operationof SuperKEKB.

INTRODUCTION
SuperKEKB [1,2] is an electron-positron collider with thecenter-of-mass energy of 10.58 GeV. This is an luminosity
frontier machine aiming the world largest luminosity of 8 ×1035 cm−2 s−1 .
The top-up filling operation is required for both the electron ring (HER) and positron ring (LER). The beam currents
become quite large like 3.6 A (HER) and 2.6 A (LER) insuch a large luminosity. The beam lifetime is short and tobe ∼5 minutes in case of LER.
We develop the archive system which archives the injection related information in pulse-by-pulse. It can be utilized
for understanding the injection condition. This is necessary
to keep efficient injection for the entire run period.
The system is designed and developed during the shutdown period between phase-1 and phase-2. It is commissioned in the early stage of phase-2 operation, and thenbecomes fully functional since April 2018. The data havebeen archived until the end of phase-2.
This report introduces the specification of archive system
and its data acquisition scheme. Then some results fromarchiver are discussed.

ARCHIVE SYSTEM
Overview
Figure 1 is the schematic view of archive system. The
system consists of database server and the module of Event
Timing System [3]. In addition, there is software which associates individual archived data as one injection information.
All archived data are collected from EPICS Process Variables (PVs) [4] with their issued time. The issued time isquoted from the CPU time of each EPICS IOC. Therefore
the variables belonging to different IOCs use the different
timestamps as the issued time.
∗ hiroshi.kaji@kek.jp

Figure 1: Schematic view of archive system: the databaseserver collects and archives the information related with theinjection via the accelerator network. The archived variables
which need to unified their issued time are once stored into
the Event IOC. Then, they are sent to the database serverwith the timestamp of Event IOC.
There is one IOC which the Event Receiver (EVR) isinstalled. The archived variables which need to use theunified timestamp as the issued time are once stored on thisIOC. Its detailed specification and usage are described later.

Database Server
The database server is based on the Control System Studio(CSS) archiver and the postgreSQL as the database management system. It is originally developed for monitoring theQCS and Belle2 solenoid magnets [5].
The standalone PC with Linux OS is employed for thedatabase server. It collects information from the remote
EPICS PVs via the accelerator network.

Event IOCThe Event IOC consists of the CPU and EVR modules
and is configured on the VME form factor. This is utilizedfor unifying the timestamps of individual archived variables.
There is the advantage to use the CPU time of Event IOCas the unified timestamp. The CPU time of all Event IOCsand IOCs for Abort Trigger System are synchronized [6].
Therefore the issued time of archived data can be comparedwith the timing of activities of above mentioned IOCs.
The other motivation to use the Event IOC is the data
buffer information. This IOC receives the several kinds ofinformation related with the injection pulse. They are theshot ID, the RF-bucket to be injected the next injector pulse(injection-bucket), and so on.
We archive the bunch currents of only injection-buckets
and some neighboring RF-buckets which are affected with
the injection kicker pulse. The injection-bucket informationfrom data buffer is utilized for this process. We can savethe disk space and the computing resource by avoiding thearchive of all bunch current monitor (BCM) information.

Figure 2: Time chart of data acquisition: the Event IOC
receives the bunch current before injection when it receives
the data buffer. That after injection is received when theBCM is processed.

Client for Monitoring and Offline Analysis
The two kinds of software are available to access theinjection database. One is the CSS monitoring client. This
has already utilized since the phase-1 operation. The several
components at the interaction point are monitored [5]. Ofcourse, we can utilize also for the injection informationmonitoring.
The other is ROOT [7]. It is the C++ base software which
is developed at CERN for the high energy physics experiments. The ROOT includes the PostgreSQL library so that
we can access our database.
The ROOT enables the detailed offline analysis as wellas the simple monitoring. We can easily program the complicated arithmetic-operation of archived data with the C++
code. For example, the individual variables archived in parallel are associated as the each injection pulse data in theoffline analysis with ROOT.

DATA ACQUISITION SCHEME
Figure 2 is the time chart of data acquisition. The EventIOC collects the BCM information twice in every injection
pulse.
The first process is launched when the EVR receives thedata buffer. The data buffer is delivered 17 ms before injection process. The bunch current at the injection-bucket iscollected from BCM IOC via the Channel Access protocolof EPICS and stored into the PV on the Event IOC. This
process is finished before injection in a enough time margin.
The second process is triggered when the objective IOCs
are processed. The BCM IOC is processed every time whenthe injection is carried out. Therefore the collected bunch
current becomes the one after injection. Typically, the BCM
IOC is processed 10 ms after the injection.
The issued time of BCM data are changed to be the one
determined from the CPU time of Event IOC. It is important
for the reconstruction of injection data performed on theROOT program.
The same thing is carried out for the last BPM at beamtransport line between the injector and main ring. The chargeof beam pulse is archived in every injection.
Note, the entire process need more than 20 ms. However
the injection frequency is limited to be less than or equal toFigure 3: An example of issued time difference of BCM
data between before and after injection: the left plot shows
the time difference of BCM. It is typically ∼27 ms. The
right plot shows time difference between BCM data before
injection and BPM data at beam transport. It is typically∼31 ms. The resultant time differences are consistent withthe processed time difference of EPICS PVs.

25 Hz in the phase-2 operation of SuperKEKB. Therefore
we have enough time for data acquisition.

RESULTS IN THE PHASE-2 OPERATIONIn this section, we introduce some results from ourarchiver. We develop the new method to monitor the injected beam current by using the data acquisition describedin the previous section and the offline analysis.
The injected current is defined as the bunch current difference of injection-bucket between before and after injection.
The bunch current data after injection is associated withthose before injection when their issued time difference isless than 40 ms. The charge of beam pulse at beam transportline also is associated in the same criterion.
Figure 3 shows the issued time difference of associatedbunch current data. The time difference is ∼27 ms and consistent with the processed time difference of EPICS PVs.
That of charge at beam transport is ∼31 ms.
An example of operation current and injected current at
LER are shown in Fig. 4. The injection current from ourarchiver shows some interesting features.
There is the fluctuation for injected current which arecaused by the instable operations of injection components,like the kicker and septum magnets. Besides, the significant
beam loss is observed in many pulses. They can be observed
since the injected current is archived in pulse by pulse. Note,
traditionally, we monitor the injected current from DCCT
in average of 1 second. The fluctuation and beam loss are
disappear in this way.
The other advantage of new injected current is it avoids
the influence of beam lifetime. There is no degradation of
injected current even though the operation current becomeslarge to be 340 mA in this run. The obvious degradation
is observed in the DCCT measurement. It is because theDCCT measures the beam current of all operation bunches
so that the natural beam loss of those bunches affects thecurrent measurement.
There are the data of bunch currents which are affectedwith the injection kicker pulse. Those bunches may be thesource of beam background. Therefore the analysis of thoseon the CSS archiver and the postgreSQL. The Event IOC
is utilized for unifying the timestamp of injection relatedvariables.
The injected current is archived in pulse by pulse. The
fluctuation and significant loss of injected current are observed with this new method. The archive is implemented
in the entire phase-2 operation.

REFERENCES
Figure 4: An example of operation current and injectedcurrent at LER: the upper three plots show the operation
current, injection efficiency at LER, and charge at beamtransport line. The injection efficiency is the kind of injectedcurrent and determined as the injected current divided bycharge at beam transport. The lowest plot is the injectedcurrent determined and archived in the new method.
bunch currents are important to understand the beam background events in the physics analysis. It is planned to bereported separately in future.

CONCLUSION
The archive system for injection information is developed
for the SuperKEKB collider. The database server is based[1] Y. Ohnishi et al., “Accelerator Design at SuperKEKB”, Prog.
Theor. Exp. Phys., vol. 2013, no. 3, p. 03A011, 2013.
[2] K. Abe et al., “Letter of Intent for KEK Super B Factory”,
KEK Report 20014-4.
[3] MRF website;
http://www.mrf.fi/index.php/vme-products[4] EPICS website;
http://www.aps.anl.gov/epics/[5] K. Aoki et al., Abstracts of CSSJ Conference, Vol. 92 (2015)p.85.
[6] H. Kaji et al., “Time Synchronization for Distant IOCs of theSuperKEKB Accelerators”, in proc. IPAC’17, Copenhagen,Denmark, 2017.
[7] ROOT website;
https://root.cern.ch/