Bitflow Coaxpress Frame Glover AIDS SuperKekb Particle Accelerator Beam Fault Troubleshooting

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July 7, 2025 – The Super Keb Particle Accelerator in Tsukuba, Japan was built to achieve the highest particle collision speed in the world, enabling the next generation of investigation of basic physics. SuperKekb is unique in adopting a nanobeam scheme that narrows the beam to nanometer scale sizes at interaction points to increase the collision efficiency of electrons and positrons using large intersection angles between impact beams.

In its quest to reach the highest collision rate in the world, SuperKekb suffers repeatedly with sudden beam loss (SBL) events. The SBL event occurs when the vertical beam current decreases by more than 10%, and within a few turns the process only lasts 20-30 ms. It is unknown what specifically invokes the SBL event. According to one theory, beam trajectory vibrations cause the beam size to significantly increase several turns before the generation of SBL. However, escalations of sizes that began earlier than beam oscillation were also observed. The increase is measured to be up to 10 times greater than the normal beam size.

The SBL is the biggest obstacle to the long-term stability of SuperKekb beam operations. It is also located side by side in the tunnel, which can seriously damage the accelerator components within the electron or positron ring. It was important to determine the source behind the SBL incident and to implement control measures.

Identify the origin of SBL

To uncover the root cause of SBL and ensure redundancy, the SuperKekb team has developed two turn-by-turn beam size monitors that operate at various wavelengths. One is an X-ray system for beam size diagnosis, and the other is a visible light monitor that focuses on beam trajectory variation and increase in size.

The 99.4 kHz revolution frequency of the particle accelerator required the use of imaging components that conform to the Coaxpress 2.0 (CXP-12) high speed standard. Data transfer rates up to 50 Gigabit per second have been achieved by aggregating four links between the Mikrotron Eosens 1.1 CXP2 CMOS camera and the Bitflow Claxon CXP4 PCIE Quad Link Frame Grabber for both X-ray and visible light systems. During data collection, the microtron camera shutter was operated with accurate synchronization with SuperKekb’s 99.4 kHz revolution frequency. Captured image data was continuously stored in Bitflow Frame Grabber’s 2GB ring buffer. It was only when the data in the ring buffer was moved to the disk server for offline analysis.

The Bitflow Claxon CXP4 can also handle 4 x 1 link cameras, 2 x 2 link cameras, or any combination of these. Each link supports data collection up to 12.5 GB/s. The highly deterministic and low latency frame grabber provides slow uplinks on all links, accurate camera sync, and 13W of safe power for all cameras per link.

By reducing the size of the camera’s area area (ROI), the X-ray monitoring system captured 99,400 frames per second, while the visible light system used ROI twice the size of the X-ray and operated at a speed of 49,700 frames per second. Beam profiles were measured in one shot every two turns, not per turn.

Beam Pattern Distinguished

Bitflow Frame Grabber’s CXP-12 transmission speed allows for accurate discrimination between the various beam patterns developed before an SPL event occurs.

Combining observations from both X-ray and visible light monitoring systems, the possibilities for SBL event scenarios have evolved. Physicists could potentially increase the theorized changes in beam tracks suddenly in the vacuum pressure in the damped section of the superkeb, which could be an irradiation possible source. In this theory, when the beam hits a vacuum component such as a beam collimator, the result is a sudden loss of beam current and SBL events. However, this is not completely clear. To explore other possibilities, SuperKekb is developing a more sophisticated X-ray beam size monitor that combines silicon strip sensors with a powerful ADC.