PROGRESS OF DIAMOND DIGITAL LOW LEVEL RF P Gu C. Christou P. Hamadyk G. B. Christian D. Spink and A. Tropp Diamond Light Source Oxfordshire UK

2025-05-02 0 0 1.3MB 5 页 10玖币

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PROGRESS OF DIAMOND DIGITAL LOW LEVEL RF

P Gu†, C. Christou, P. Hamadyk, G. B. Christian, D. Spink and A. Tropp, Diamond Light Source,

Oxfordshire, UK

Abstract

The first version of digital low level RF (DLLRF) for

the Diamond Light Source storage ring and booster was

developed with ALBA Synchrotron. Six systems have

been built so far. Two of them are in routine operation

controlling two normal conducting HOM-damped cavities

in the Diamond storage ring. A third system is being used

for cavity testing in the RF test facility (RFTF). The

fourth system is being commissioned to control the sec-

ond normal conducting booster cavity. The fifth DLLRF

system is being prepared for the third normal conducting

RF cavity in the storage ring.

A new DLLRF system based on SIS8300-KU with

RTM has been developed and tested in the last few years.

We are aiming to develop a common platform for the

different RF systems in Diamond, including the storage

ring, the booster and the Linac. It will also be our baseline

design for the future Diamond II. Firmware, software and

supporting hardware have been developed and tested. The

Linac version with arbitrary waveform generator mode

was tested successfully to generate flat top pulse from

SLED in the high power test in the Linac. The storage

ring version was also tested successfully in RFTF.

INTRODUCTION

Diamond Light source has been providing beam for us-

ers since 2007. We have three major types of RF systems,

the linac RF system, booster RF system and storage ring

RF system. The linac RF system works at about 3GHz,

while booster RF system and storage ring RF system

work at around 500MHz. The booster operates with two

5-cell PETRA cavities. The storage ring RF system con-

sists of two superconducting RF cavities and two normal

conducting HOM-damped (NC) RF cavities, with a third

normal conducting cavity being commissioned. A first

version of DLLRF system has been developed together

with ALBA in 2015. Nutaq Perseus 601X advanced mez-

zanine card (AMC) with Xilinx Virtex 6 FPGA was used

as the core hardware. We have built 6 systems so far. Two

systems have been operational with two NC RF cavities

since 2019. The DLLRF system for the second booster

cavity was installed and tested successfully with beam

this year. The DLLRF system for the third NC cavity in

the storage ring is being commissioned.

Following the successful experience of the first version

of DLLRF and as better hardware became available on

the market, we started developing our new DLLRF. The

new design maximizes the common hardware compo-

nents for all Diamond RF systems. Struck SIS8300-KU

with rear transition module (RTM) was selected as the

core hardware. RTM is the only difference between

3 GHz DLLRF (Linac) and 500 MHz DLLRF (booster

and storage ring). We have designed and built the new

DLLRF systems. The new DLLRF systems have been

tested successfully in the Linac and in RFTF controlling a

NC cavity. The Linac version has demonstrated flat-top

output pulse from SLED RF pulse compressor. The new

DLLRF is our baseline design for the RF systems of Di-

amond II, including DLLRF for harmonic RF cavity.

DEPLOYMENT OF FIRST VERSION

DLLRF

The description of our first version DLLRF system can

be found in [1]. It was based on the Micro Telecommuni-

cations Computing Architecture (MicroTCA) standard,

for its reliability, modularity and scalability. A commer-

cial advanced mezzanine card (AMC), Perseus 601X with

Virtex6 FPGA from Nutaq, is used as the core processor

of the control algorithm. 16-Channel 14-bit ADCs and 8-

channel 16-bit DACs on FPGA mezzanine cards (FMC)

are used for analogue inputs and outputs.

Clock and local oscillator (LO) were generated locally

from 500 MHz master oscillator (MO) in each system. RF

signals are mixed with 479 MHz LO signal to generate

20.8 MHz IF signal. The IF signal is filtered before being

sampled by ADC at 4 times the IF frequency. In the up-

conversion chain, the DAC directly generates 20.8 MHz

IF signal, which is mixed with LO, filtered and amplified.

There is a PIN switch in the up-conversion unit that can

be triggered by an interlock. A digital patch panel was

also included to interface digital signals between the

LLRF and other systems of the RF plants (tuner motor

controllers, PLC controllers, MPS, etc).

Since its first test in the Diamond booster, the DLLRF

system has been tested in the RFTF controlling NC RF

cavity. Two NC RF cavities were installed in the storage

ring in August and November 2017 in straights adjacent

to the existing RF straight. Two DLLRF systems were

then deployed for the control of two NC RF cavities in the

storage ring in 2019. One installed DLLRF system is

shown in Figure 1. The second 300 kW amplifier was

split to feed the two NC RF cavities through 9-3/16 inch

coaxial transmission line.

The control precision was measured with beam. The

DLLRF can achieve 0.2% RMS in amplitude and 0.02

degree in phase. Phase noise of the closed loop between

10 kW and 60 kW, measured at a diagnostic point in the

DLLRF front end, is similar to that of the oscillator used

to drive the system with the addition of some noise in the

1 kHz to 10 kHz range. Spurs are visible at harmonics of

mains frequency in both oscillator and DLLRF measure-

ments, as shown in Figure 2.

___________________________________________

† email address pengda.gu@diamond.ac.uk

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PROGRESSOFDIAMONDDIGITALLOWLEVELRFPGu†,C.Christou,P.Hamadyk,G.B.Christian,D.SpinkandA.Tropp,DiamondLightSource,Oxfordshire,UKAbstractThefirstversionofdigitallowlevelRF(DLLRF)fortheDiamondLightSourcestorageringandboosterwasdevelopedwithALBASynchrotron.Sixsystemshavebeenbuiltsofar.Twoofthemareinroutin...

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PROGRESS OF DIAMOND DIGITAL LOW LEVEL RF P Gu C. Christou P. Hamadyk G. B. Christian D. Spink and A. Tropp Diamond Light Source Oxfordshire UK

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