Fill-pattern Control System for KEKB Eiji KIKUTANI KEK (Factories03, Oct. 2003 SLAC) 11/21/2018 Factories03

Plan of talk What is the Fill Pattern Control System? KEKB fast timing system (brief) Architecture of the system Software system Summary 11/21/2018 Factories03

1. Introduction What is the Fill Pattern Control System? 11/21/2018 Factories03

Fill Pattern is important ! Fill pattern ----- which rf-buckets are filled with beam, while which are not --- Fill pattern is one of the important para-meters in operating the rings, because strength of the coupled-bunch instability is strongly depends on the fill pattern, however, … it is practically hard to find an ideal pattern from calculations. 11/21/2018 Factories03

What is a “Fill Pattern control system”? We must find the ideal filling-pattern with the trial-and-error method, it means ….. we need a fill pattern control system, which should be operator-friendly flexible for modification 11/21/2018 Factories03

Fill pattern with mod. 4-bucket 11/21/2018 Factories03

Structure of the fill pattern control system fill-pattern generating mechanism + bucket selection system 11/21/2018 Factories03

What is “the fill pattern generating mechanism”? An environment for generating a suitable fill pattern easily creates a table of rf-buckets which should be filled with beam (the fill-pattern table) from given fill pattern 11/21/2018 Factories03

What is “the bucket selection system”? distributes the linac beam-pulses into the ring rf-buckets, and consequently realizes a desired fill pattern in the rings a sub-system of the KEKB fast timing system Real time 11/21/2018 Factories03

2. KEB fast timing system 11/21/2018 Factories03

KEKB fast timing system We have no damp-ing rings. Phase relation between the linac-rf and the ring-rf should be finely controlled to main-tain the injection rate high. 11/21/2018 Factories03

RF freq. of the linac and the rings Each rf-signal is obtained by frequency-multiplying the common signal of 10.38MHz 10.38MHz x 275 =2856MHz (for linac) 10.38MHz x 49 =508.9MHz (for rings) 11/21/2018 Factories03

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Conceptual Block Diagram of the KEKB fast timing system 11/21/2018 Factories03

Timings for the injection (to maintain good injection) 11/21/2018 Factories03

Method for the bucket selecting Control the timing triggering the linac gun the timing is controlled by delay modules named “TD4”. 11/21/2018 Factories03

The subrack of the Linac IOC 11/21/2018 Factories03

3. Architecture 11/21/2018 Factories03

Architecture of the Fill Pattern Control System Basically, system is constructed under the EPICS environment The system consists of 3 parts. The delay control (TD4) part, (in linac) (Linac IOC) the Operator-communication-part (Op-IOC) the Bunch-Current monitor part (BC-IOC) 11/21/2018 Factories03

delay modules bunch-current monitor Central control room linac 11/21/2018 Factories03

Architecture of the fill pattern control system (cont.) These are connected with a dedicated communication system with optical fiber cables which is realized with a commercial product Shared Memory System (Advanet Company in Japan) 11/21/2018 Factories03

Shared Memory System http://www.advanet.co.jp Communication Port/module 1 Communication System Fiber channel Bit rate 250Mbit/s # of connectable of boards in a loop 255 (max.) Wiring Distance between Board 1km (max.) Connector SC Size of Shared Memory 128Kbyte (Expandable to 1M/2M/4M/8Mbytes) 11/21/2018 Factories03

Shared Memory System (VME memory board) 11/21/2018 Factories03

Connection of the three IOCs 11/21/2018 Factories03

4. Software 11/21/2018 Factories03

Software structure of the fill pattern control system 11/21/2018 Factories03

Software in the Op-IOC Communicates with operators accepts the fill patterns from the built-in panel, as well as the fill pattern files generates the fill pattern table (in Shared Memory System), in accordance with the fill pattern specified by the operator 11/21/2018 Factories03

Pattern generation 11/21/2018 Factories03

The panel for the built-in pattern generator. 11/21/2018 Factories03

A panel for fill pattern generation (custom) 11/21/2018 Factories03

Software in the Linac IOC a Vx-Works real time task essentially no I/O, except for the Shared Memory System “fetch” the bucket address to be filled from the shared memory, and set the delay Two operation modes (BCE and non-BCE) 11/21/2018 Factories03

Operation modes of the bucket selection system Bunch current equalizing (BCE) mode Compares bunch current of each bucket, and fill the beam into the bucket with smallest current (except for those near the last-filled buckets) The comparison is done pulse to pulse (every injection trigger) switch on/off easily Non-BCE mode Ad (this pulse) = Ad (last pulse) + some prime number 11/21/2018 Factories03

Timing shake-hands of the IOC tasks A task in the BC-IOC is triggered by the injection triggering signal. After writing the bunch-current information into the shared memory, it generate the interrupt signal to the Linac-IOC A task in the Linac-IOC is triggered by this interrupt signal 11/21/2018 Factories03

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Uses of the bunch-current information Simple bunch current monitoring (relative bunch-current) For bucket selection. Bunch Current Equalizer (BCE) is working High bunch-current alarming 11/21/2018 Factories03

The bunch-current board Bunch-current information is stored in the “memory board” ----- a by-product of the KEKB bunch-feedback systems. The stored information is read out by the trigger signal of the injection kicker No averaging process 11/21/2018 Factories03

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Bunch-current detector 11/21/2018 Factories03

Recent improvements For positron beam, we started use the 2-bunch acceleration in the Linac In the positron linac, two bunches, separated by 98ns, are accelerated and injected to the ring. It increases the injection rate of positrons by a factor ~2. 11/21/2018 Factories03

Two bunch acceleration in the Linac 11/21/2018 Factories03

Two bunch acceleration Real-time two/single switch Two-bunch acceleration ==> BCE off Every 50-th pulse : single bunch acceleration ==> BCE on (equalization) variable 11/21/2018 Factories03

Summary KEKB Fill Pattern Control System is working for realizing a desired fill patterns in the rings. The BCE technique works very well 2-bunch acceleration scheme works with a satisfactory performance 11/21/2018 Factories03