Beam Position Monitor
The Brazilian Synchrotron Light Laboratory (LNLS) is currently designing a third-generation 3 GeV low emmitance synchrotron light source in Campinas, Brazil, called Sirius, with commissioning due to 2018. The main parameters of the machine are:
| Parameter | Value | Unit |
|---|---|---|
| Beam energy | 3.0 | GeV |
| Injection energy (top up) | 3.0 | GeV |
| Beam current | 350 | mA |
| RF frequency | 499.658 | MHz |
| Harmonic number | 864 | - |
| Natural bunch length | 8.8 | ps |
| Natural emittance | < 0.24 | nm.rad |
| Circumference (storage ring) | 518.4 | m |
For more information about the Sirius project please refer to this link.
In the context of the Sirius project, the Beam Diagnostics Group (DIG) of LNLS has been called to develop a beam position monitoring system (BPM) which must provide electron beam position real-time monitoring, triggered data readouts, fast orbit feedback capabilities and advanced beam diagnostics tools for the new accelerator’s injector and storage ring. This project is primarily intended to deliver a BPM system for the Sirius machine. Nevertheless, it is made open for the particle accelerators community and general public for design reuse and collaborative development, under the CERN Open Hardware Licence and GPL-derived licences.
The BPM electronics hardware is composed of 3 main subsystems: RF front-end ((RFFE), 130 MS/s ADC board (ADC) (or 250 MS/s ADC board) and digital back-end (DBE).
The RF front-end is designed for button BPM pick-ups and must allow nonlinearity lesser than 0.002 dB on top-up operation with maximum gain of 60 dB. Bandpass filtering must provide 45 MHz, 80 dB bandwidth, around the 500 MHz beam’s main frequency (customizable for other beam frequencies). 2x2 RF channel switching is used for non-linearity and slow gain drifts compensation. Board temperature control is available to minimize ambient temperature variations effects on position measurement and RF channel health inspections.
The ADC board is a FPGA Mezzanine Card (FMC) module fully compliant to the ANSI/VITA 57.1 standard, providing 4-channel 16-bit 130 MS/s (LTC2208IUP) or 250 MS/s (ISLA216P25) optimized for a 500 MHz center frequency. Clocking can be phase-locked to external reference clock (with fine frequency tune capability) or direct clock inputs (from front panel or FMC clock) as well as bi-directional (configurable) trigger.
The DBE is a crate-based system which integrates in a single enclosure the FPGA processing boards for beam position sensor data processing, data acquisition and advanced diagnostics, fast orbit feedback (FOFB) processing boards for feedback control algorithm processing, a dedicated CPU for control system interface and RF front-ends control. The FPGA boards are connected to the CPU via 4 lanes of PCIe Gen 2 link. The DBE relies on the PICMG® MicroTCA R1.0 standard (MicroTCA.4), using COTS crates and infrastructure boards such as MCH and CPU. Besides power, cooling and IPMI infrastructure, the MicroTCA.4 backplane provides JTAG chain access to all individual slots, GbE and PCIe switches, as well as multigigabit point-to-point connectivity between slots, 8 M-LVDS triggers, and 2 low-jitter radial clocks.
The FPGA board, a.k.a. AMC FMC Carrier (AFC), is fully compliant to PICMG® AMC R2.0 standard (AMC.0, AMC.1, AMC.2) and features one Xilinx Artix-7 200T FPGA device, 2 FMC high-pin count slots, 2 GB SDRAM (32-bit interface), White Rabbit support and standalone operation capability.