After the completion
of operation corresponding to the phase B, the maintenance activities have started
mid of August as planned alongside the preparation of the next phase: phase B+.
In this long maintenance period, it is important to carry-out both the curative
maintenance of components that were malfunctioning and the preventive
maintenance to ensure a better reliability and availability of the systems for the
next operation campaigns. The maintenance activities are planned targeting to
resume Injector continuous wave operation and Radio-Frequency Quadrupole (RFQ)
conditioning before end of 2019, so that LIPAc operation can restart in the
second quarter of 2020. In this first period higher priority has therefore been
assigned to the Injector and RF/RFQ systems maintenance.
the Diagnostics-Plate and of the vacuum systems have also started; maintenance
of the Medium-Energy Beam Transport line (MEBT) are planned in December. Specific
activities on the beam instrumentation will be carried out in November with EU
experts from CEA and INFN on-site. The final beam instrumentation checkout will
take place after the installation of the MEBT extension line.
The maintenance of the ancillaries is on-going and
many activities have already been completed, such as electrical network
distribution, secondary cooling system, Personnel Protection System, Accelerator
vault crane. The cryoplant maintenance activities will be carried out in the
first quarter of 2020.
of LIPAc into its future phase B+ configuration, with its High Energy Beam
Transport line (HEBT), is also the goal of this maintenance period. The MEBT
extension line has been designed to transport the beam at 5 MeV instead of
the cryomodule. It is composed of quadrupoles to focus the beam, steerers to
correct its trajectory, Beam Position Monitors to monitor the beam orbit, a
vacuum chamber to host a Residual Gas Bunch Length Monitor, Beam Loss Monitors
and turbo-pumps for vacuum pumping. The components of the MEBT extension line are
currently being procured or manufactured.
The Low Power Beam Dump which was used during
phases A and B will be removed. The HEBT is positioned in its final position together
with the Diagnostics Plate, and the LIPAc Beam Dump for full beam energy will
be connected to the beam line.
The deuteron (D+) beam commissioning has been ongoing
since two months, and we achieved a 125 mA beam acceleration by the Radio
Frequency Quadrupole (RFQ), and transported to the Low Power Beam Dump (LPBD)
on the 24th of July, 2019. The data was obtained in pulsed mode
operation of ion plasma source with 1 ms length and 1 Hz repetition
The beam current range was varying from 50 to 140 mA at the
entrance of RFQ, and 90% transmission through the RFQ was measured for a maximum
current of 125 mA (measurement taken at the end of the beam pulse shape) and for
a rated RFQ cavity voltage of 132 kV.
The detail of the accelerated beam characteristics is under
investigation and the commissioning phase is still ongoing.
This significant outcome demonstrates that all the components of the
LIPAc accelerator in the phase B configuration meet the design requirements. This
achievement gives us confidence for the future and the next step toward continuous
wave operation at 5 MeV with its high energy beam transport line.
The proton characterization at 2.5 MeV was completed on April 30, 2019
(Phase B1). During this phase, with an extracted current of 88 mA and 300
µs maximum pulse length from the injector, a maximum current of 57 mA was accelerated in the Radio
Frequency Quadrupole (RFQ) with a transmission of 93 % through RFQ and beam
transport line up to the Low Power Beam Dump (LPBD).
The RFQ was conditioned for proton level operation, which
requires a field of about 70 kV to accelerate the protons. In the case of
the deuteron operation (next phase B2, and nominal condition of the machine),
the cavity needs to be conditioned to reach a maximum field of 142 kV. The
conditioning is still on-going to reach that field level with pulses up to 300 µs.
Instrumentation has also demonstrated to be operational. Further improvements are ongoing which should ease beam operation and allow data analysis with
comparison to beam dynamics models.
As an example, the above figure on the left shows the
measurement of beam profiles, providing the shape of the beam. On the right,
the beam position in space is monitored.
Project Committee (PC#23) was held at Rokkasho IFERC Site on March 18th
and 19th, during which an update of the project status was presented
as well as the outlook from 2019 onward.
main topics discussed were the progress since the last PC#22 with the achievement
of the annual maintenance campaign, the completion the HEBT and Beam Dump installation
in the accelerator line and the resumption of the Beam Operation with proton
beam and the first deuteron injection into the RFQ. The preparatory work for
the assembly of the Cryomodule in the clean room at Rokkasho was also presented.
The PC members in the LIPAc Control Room participating to the beam operation
The maintenance period was completed early 2019 and the acceleration of proton beams up
to 2.5 MeV was resumed on 20 February. A transmission of 95% through the RFQ
was achieved with an input beam current of 7 mA and 0.3 ms pulse length. By
using such a beam, the phase tuning of the two bunchers installed in the MEBT
was performed successfully. The basic beam diagnostics, beam current monitors
(ACCT) and beam position monitors (BPM), were used regularly for beam
commissioning, and the beam profile measurement was started by using a
non-interceptive device (Fluorescence Profile Monitors) and an interceptive one
(Secondary electron emission grid monitors). The latter one is also used to measure
the beam emittance with a slit insertion.
After completing the first beam operation stage, and while profiting of the stop of the machine for the scheduled maintenance, the first LIPAc Commissioning and Beam Operation workshop was organized at Rokkasho site.
During 2 days, the accelerator scientists and experts from Japan and
Europe exchanged about the experiences and outcomes of the first beam operation
campaign with the LIPAc RFQ accelerator, and the difficulties encountered in
the LIPAc commissioning activities. Discussions also addressed the preparation
of the second beam campaign, scheduled from early next year. Furthermore, the
steps ahead were discussed to prepare the assembly, installation and
commissioning of the last accelerating stage (including the superconducting
cavity SRF Linac, which will increase the deuteron energy up to 9MeV).
The next workshop with a similar format will gather again the LIPAc community after the completion of the commissioning Phase B (5 MeV, 125 mA, D+,0.1% DC, including the commissioning of the RFQ and Buncher cavities, as well as the beam instrumentation).
On November 12th, 2018, we were honored by the visit of the French Ambassador, his excellency Laurent Pic, and his delegation at Rokkasho. We were given the chance to present the activities performed at the IFERC site…
… followed by a tour focusing on the LIPAc activities. It was explained that these activities are conducted in the frame of the Broader Approach Agreement and the IFMIF/EVEDA Project. Emphasis was given to the substantial contribution from the French institute CEA being a key part of the European contribution.
The “Francophone” working at Rokkasho were given the opportunity to share their experience about living in the north of Japan and working in this international partnership.
The ambassador was favourably impressed by the activities ongoing at Rokkasho under the European – Japanese collaboration and confirmed the strong interest of France in this project.
Before leaving, he promised that he will come back soon to learn more about the progress in the commissioning of the accelerator systems.
On October 16th, 2018 the transfer of ownership of the Beam Instrumentation, Medium Energy Beam Transport Line and the Radio Frequency Qaudrupole were signed between F4E and QST with the presence of the respective European Voluntary Contributors CEA (Saclay) , CIEMAT (Madrid) and INFN (Legnaro).
This equipment was delivered by the European Voluntary Contributors and transfered to F4E, the EU Implementing Agency of the Broader Approach project, as they were shipped to Rokkasho. The transfers of ownership to QST, the JA Implementing Agency, were cleared out with the recent completion of the individual commissioning of each system.