Data Master, UNILAC PZ and Various Gateways - An Overview

Introduction

Today (December 2021) there exist two Machine Timing Systems at GSI. First, the General Machine Timing (GMT) system for FAIR is based on White Rabbit and supplies 'timing' to SIS18 and all downstream parts of the facility, including the two storage rings ESR and CRYRING as well as the FRagment Separator (FRS), transfer lines ... . Second, the so-called UNILAC Pulszentrale (UNIPZ) is based on the 'MIL-Eventbus' and supplies 'timing' to the injector UNILAC including all ion sources, the Experimental Hall (EH) and most of the Transfer Channel (TK) towards SIS18.

Timeline

Prior 2018

Figure: Timing systems based on the 'MIL Eventbus' prior 2018. Left: UNIPZ. Right: SIS-PZ and ESR-PZ. Middle: SIS-PZ and UNIPZ are synchronized via MIL-bus.

The figure aboves depicts the timing system at GSI prior 2018. It is based on the 1 MBit/s MIL-STD-1553 'MIL-Bus' which was enhanced by additional interrupt lines, this is a master-slave architecture. The timing system is a purely event-based system. At GSI, the master is called Pulszentrale (PZ). On-time, it sends telegrams of 16bit length to the network. The telegrams include a 4 bit machine number (virtual accelerator), an 8 bit event number and 4 bits for additional information.

There existed nine timing areas. The linear acclerator is a complex machine that had seven timing areas each with its own PZ; the seven PZs are coordinated by one so-called Super-PZ. In the figure above, all these PZ (masters) are grouped together in one block named 'UNIPZ'. Two additional timing areas had been implemented, one for each ring machine. The masters had been called SIS-PZ und ESR-PZ. For injecting beam from UNILAC into SIS18, the SIS-PZ was linked to UNIPZ by MIL-bus.

More information on UNIPZ is available here.

Since 2018

A new General Machine Timing System (GMT) based on White Rabbit has been developed for the upcoming FAIR facility. It is based on White Rabbit, which is an enhancement the Precision Time Protocol IEEE 1588 implemented on top of Ethernet. The GMT is a time based system. More information on the GMT is available here.

Figure: SIS18-PZ and ESR-PZ are replaced by the Data Master (DM, blue box, right) and a White Rabbit network. MIL-Events are provided to existing equipment by means of a White Rabbit to MIL Gateway (small blue box, right). A 'DM-UNIPZ' gateway serves to synchronize the DM and UNIPZ (blue box, middle).

Starting with the beam-time, the machine timing of SIS18, ESR, HEST ... is exclusively controlled via the new GMT.

Still today, there is a need of supplying old front-ends with Events via MIL-Eventbus. This has been achieved by implementing gateways that listen to the White Rabbit network and - on-time - send events to the existing MIL-bus line for SIS18 and ESR (shown as small blue box on the right). More information on this gateway is available here.

Synchronization between SIS18 and UNILAC is achieved via 'Gateway DM-UNIPZ', which basically just sits between UNIPZ and DM converting MIL to Ethernet and Ethernet to MIL telegrams. More information on this gateway is available here.

Since 2021

Figure: The UNIPZ has been extended by a White Rabbit interface (small blue box, left).

On the long run, White Rabbit based timing is required at UNILAC too. In 2020 it was decided, that an intermediate solution shall be implemented. This solution is called WR-UNIPZ and in operation since January 2021. More information is available here.

Future

Figure: Future GMT.

In the future, the UNIPZ shall be replaced by a solution that is part of the GMT and the pLinac is integrated as a second injector. However, it is expected that old front-ends requiring the MIL-Eventbus will continue to exist and White Rabbit to MIL gateway must be implemented. Moreover, the hardware of the Data Master requires a serious upgrade that might be implemented as a cluster of many nodes.

-- DietrichBeck - 08 Dec 2021