蓄積リング/Storage ring (Accelerator Group )

Main Parameters

Two LSS and two SSS are used for beam injection, rf cavities, 3-pole wiggler + X-ray pinhole camera system, DCCT, and bunch-by-bunch feedback system.

There are 14 undulator section at LSS and 14 multi-pole-wiggler (MPW) section at SSS at maximum.

Details can be found from the conceptual design report, and the commissioning result paper (Phys. Rev. Accel. Beams 28, 02071 (2025)).

Typical electron beam size at the insertion device section is 121um (horizontal) and 5.8um (vertical) in design, assuming 1% coupling.

A 5.44-m long straight section (for undulators) is left side of the figure. A 1.64-m short straight section (for MPWs) is center of the figure.

This is a centrally symmetrical design cell.

Bending magnets

Four B-Q combined bending magnets are installed per cell, for a total of 64 magnets. They are connected in series to a single power supply, with no auxiliary power supplies or trim coils.

Quadrupole magnets

Ten quadrupole magnets are installed per cell, for a total of 160 magnets. Some of them are connected to the auxiliary power supplies.

Sextupole magnets

Ten sextupole magnets are installed per cell, totaling 160 magnets.

Some of them have independent auxiliary power supplies in each pole pair, in order to use as a steering magnet.

Thanks to the highly precise magnetic alignment, the 1st beam turn was successful without any steering magnets at the commissioning phase.

• “Commissioning of a compact multi bend achromat lattice NanoTerasu: A new 3 GeV synchrotron radiation facility”, S.Obara et. al., Phys. Rev. Accel. Beams 28, 02071 (2025)

Storage ring vacuum reaches O(10^-8) Pa.

At the first user operation in April 2024, the beam lifetime was approximately 10 hours under a 200 mA condition.

Four TM020-mode used Higer-Order-Mode (HOM) damped cavities (Nucl. Instr. Meth. A ,1064, 169418 (2025)) are installed.

Operation techniques are also developed as Rev. Sci. Instrum. 96, 063303 (2025) .

• “Compact HOM-damping structure of a beam-accelerating TM020 mode rf cavity”, H.Ego et. al., Nucl. Instr. Meth. A ,1064, 169418 (2025)
• “Frequency offset system to feed RF power to accelerating cavity with keeping field uniformity”, T.Ohoshima et. al., Rev. Sci. Instrum. 96, 063303 (2025) .

Seven Beam Position Monitors (BPMs) are installed per a cell.

NanoTerasu adopted off-axis injection. Four pulsed-kicker magnets and one in-vacuum pulsed septum magnet are installed into one of the long straight sections as the injection point. The stored beam has an approximately 7.5 mm bumped height in horizontal.

Top up injection fills about 0.3 nC per shot from injector LINAC.