1

Report from Control Group
Hiroshi Kaji

2

New delay module for Event Receiver
The delay step for EVR is, usually, 8.7ns (= One clock of FPGA).
We installed the new delay module with more precise delay setting.

UNIV-TTLDLY(New fine delay module)

Arbitrary delay in the 400ps step
It is equipped in the universal slot.
We developed the EPICS device support for it.

3

Delay control for DR extraction kicker
The Event IOC for the DR-extraction trigger was upgraded in the 2022ab run.
- A few nanosecond of the timing shift caused by the pulse-to-pulse modulation is corrected.
- The fluctuations of the kicker angle and the x-orbit are suppressed.
Beforeupgradeafterupgrade
x at SP_DC_4 (1st-bunch)x at SP_DC_4 (2nd-bunch)

Data were taken at thefirst BPM after DR.

4Bunch Current unbalance in 2-bunch injection
Two-bunch injection is carried out for LER in the 2022ab run.
⇒ Sometimes, the bunch current became unbalanced.

In the current Bunch selection system, Bunch Current Equalizing (BCE) is not
implemented in the 2-bunch injection.
It is upgrade plan for LS-1.

5No. of injectionsPossibility of BCE in the 2-bunch injection
It is the upgrade plan of Bucket Selection.
The difference in the total # of injections in 8-hours
comes from the difference in the lifetime.
It depends on the bucket spacing.
The cyclic behavior in the 49 RF-buckets is seen on
the left figure.
H. Kaji, et al., Proc. of the 18th Annual Meeting of PASJ, TUOB01, August 9 - 12,2021, QST-Takasaki Online, Japan=> It is good condition for the two-bunch BCE.
(Note, the bucket spacing of injection bunches is 49.)
In the two bunch injections,
The first- and second-bunches should have similar
lifetime.
The two bunch BCE is effective in such condition.
It will be prepared during LS-1.

6Application of White Rabbit
Event Timing System is traditionally utilized for the accelerator operation.
- It realized the simultaneous top-up filling operation for colliders andlight sources (4 rings).
- The new-type investigation systems for injection and abort have beendeveloped with the timestamp synchronization.
- The sophisticated DR operation is realized with the distributed bus bit.
White Rabbit is utilized to improve the second and third functions.
- The distributed TDC system is operated to investigate the source of theSudden Beam Loss accident. More TDCs will be installed during/after LS-1.
- More precise abort request timestamp will be installed during LS-1.
- Beam Gate will be partially upgraded during LS-1.
- We developed the PCIexpress-type EPICS IOC
and are working for the VME IOC.

7

Distributed TDC system@SuperKEKB
Distributed TDC system collects the signal from the beam loss monitors.
⇒ determine the duration of the injection background.
⇒ determine the beam bunch that causes the beam loss.
⇒ determine the first loss position in the Sudden Beam Loss accident.

The timestamp of all TDC nodes are precisely synchronized with GPS.

SPEC4PPS
10MHz

GPS receiver

SPEC7SPEC6

We collect all information via EPICS PV and record
on Archiver Appliance.

8

Loss Monitor Station
Loss monitors with precise time resolution
are installed by Belle II group.

WR slave node
Picoscope
Disc.
Level

IP loss monitor station
HV- The signal from loss monitor is divided in two.
- One put into the oscilloscope to record waveform.
- The other put into White Rabbit to know the precise timestamp.

Node at Tsukuba B4 floor9Injection background
D06H3

Injection timing

Beam loss is observed at the horizontal
collimator in the first turn.

D06V1

(ms)

Then, that at the vertical collimatoris appeared behind.
⇒ Evidence of the XY coupling

D06V2

(ms)

Input timing is compared between
the injection trigger and the signals
from the D06 loss monitor.

(ms)

Data will be utilized to understandthe injection condition.

10Bunch number detection
The ID of bunch that causes the beam loss canbe evaluated by the time relation between therevolution and the signal from the loss monitors.
Injection background give us the goodcalibration of the timing relation.

Dtrev (ms)Dtrev timing offset for the #0-bucket- D06H3:+8.842 ms- D06V1:+8.817 ms- D06V2:+8.972 ms- D02V1:+2.263 ms

Injection-Bkt#Note, this relation is valid also for the stored bunches.

11Sudden Beam Loss data@Tsukuba B4
The landmarks of the bunch# and timestamp are attached on
the waveform of the beam loss signal.
⇒ The waveform can compared with those from other loss
monitors and the BCM data.

Picoscope (ch3)

BCM data

12

Direct comparison of loss monitor signals
The raw signal from the loss monitors can be compared directly withthe White Rabbit timestamp.

The first beam loss position in the Sudden Beam Loss accident can be determined.

13

Measurement of abort request timing
One of the advantages of SuperKEKB against KEKB is the abort timestamp.
The abort timestamp helps the abort study.
S. Sasaki, et al., in Proc. ICALEPCS2015, MOPGF141, Melbourne, Australia
H. Kaji, et al., in Proc. IPAC17, THPAB113, Copenhagen, Denmark

To advance the abort study, we put distributed TDC node for all Abort Trigger modules sothat the synchronization timestamp becomes accurate to be 8ns.
We can know
- more precise detection of the first beam loss position.
- how many turns the injection bunch traveled before abort.

Syn. accu.
Inter-module

100ns – 1msInjection

<40ms

14

Beam Gate upgrade with White Rabbit
The enable/disable control of the pulse components is implemented by Beam Gate.
It is for the starting/stopping the beam injection.

There are difficulties for the synchronized control between the gun and the injection
kickers.
- LER: Injections with unequal interval makes the unequal DR storage time (i.e. 23Hz).
- HER: The latency in the RF gun control from Beam Gate is always fluctuated.
All logics are installed on the master IOC of the Event Timing System.
- It is difficult to revise during the operation period. The system is vital for our project.
- The only developer can revise the system. It needs the special knowledge.
H-①: RF gun ON/OFF （After 0-80ms from Beam Gate. It is not stable.）
L-①: Thermal gun and DR Inj. kicker ON/OFF

L-②

L-①

L-②: DR ext. and LER inj kickers（80 or 140ms after L-①. It is unknown.）

H-②: Inj. kicker ON/OFF （just after H-①）

White Rabbit will be utilized for transferring the Beam Gate signal with arbitrary delay.
⇒ Test has been done at ATF. See next slide.

15

New Beam Gate signal with White Rabbit
https://atf.kek.jp/atfbin/view/Main/PublicILCandATF

SuperKEKB ATF
Operation
Interval

20ms

160ms

DR storagetime

At least
40ms

220m

ATF (Accelerator Test Facility) has the similar specification.
- The DR storage time is longer than the linac operation interval.
- It is good condition for the study of our Beam Gate system.
And they will be operated from 2022 Autumn to 2023 Autumn.

Control triggers for
Pockel cell

Control triggers forExt. kicker magnet

16

Beam Gate test at ATF
Beam Gate OFF

Beam Gate ON
Beam Gate for laser

6.125Hz before DR

100ms

Beam Gate for FF
6.125Hz after DR

This system is employed since October 2022.
More studies are on-going.
- We plan to install for HER (LINAC and D08) during LS-1.
- Then, the LER installation will be followed.

17Software release
The EPICS device support is developed and released on the White Rabbit official site
- SPEC + FMC-DIO
https://ohwr.org/project/fmc-tdc/wikis/how-to-set-up-the-spec-and-fmc-dio-with-epics- SPEC + FMC-TDC
https://ohwr.org/project/fmc-tdc/wikis/how-to-set-up-the-spec-and-fmc-tdc-with-epics

Networking and Computing
Networking
SuperKEKB accelerator control network is
separated from the Office Network by afirewall.
Most of the instruments connect to theSuperKEKB network, and a few serverconnect office network.
All main servers and storages are changed
to 10GBASE-T connection from this summer.
ComputingThe blade server has been used from KEKB
era, but due to the end of maintenance,
server and storage are updated.

Update Server and Storage
ServerWe adopted rack mount type servers, andoperates using virtual machines in the server.
Storage
We adopted “zfs” file system and the storage
is equipped with SSDs with a capacity of 20TB.

ServersStorages

By making various devices redundant, weenhanced fault tolerance.
• RAIDZ2 (double parity)• Two Power Supplies• Two Controller for fail over and one
backup node.
• backup every 15 minutes• UPS

Virtual Machine Management•

We adopted virtualization technology with
“KVM” to isolate the execution environment
for each application.

•It is also sustainable so that environment canbe maintained even if the hardware isreplaced.

•The virtual machines are running on six rack
servers to keep the load balance.

•We are planning to locate the image of VMs
at NAS to enable live migration (currentlystored locally).

Host Machine

Host Machine

VM(softIOC)

VM(web)VM(user develop)

VM(SQL)NAS

Host Machine

……

21

Summary
The Event IOC for the DR-extraction trigger was upgraded.
- Small timing shift caused by Pulse-to-pulse modulation is corrected.

The BCE in the two bunch injection will be performed after LS-1.
The application of White Rabbit is enhanced.
- The distributed TDC system is utilized for the loss monitors with theprecise time resolution.
- Beam Gate will be upgraded. The test operation of the prototype isongoing at ATF.
- The precise abort timestamp will be provided.

The EPICS device support for the above upgrade was developed andreleased.
The workstation and storage servers were upgraded.
- They have already been available for users.
- All services are running on the virtual machine. It give us flexibility
in maintenance.