MATLAB Scripts for RF Commissioning at the LANSCE LINAC Sungil Kwon A. Archuleta L. Castellano C. Marchwinski M. Prokop P. Van Rooy P. Torrez Los Alamos National Laboratory Los Alamos NM USA

2025-04-27 0 0 910.81KB 5 页 10玖币

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MATLAB Scripts for RF Commissioning at the LANSCE LINAC*

Sungil Kwon†, A. Archuleta, L. Castellano, C. Marchwinski, M. Prokop, P. Van Rooy, P. Torrez

Los Alamos National Laboratory, Los Alamos, NM, USA

Abstract

The linear accelerator (LINAC) at the Los Alamos Neu-

tron Science Center (LANSCE) consists of Pre-buncher,

Main-Buncher, low-energy beam transport (LEBT), four

201.25-MHz Drift Tube Linacs (DTLs) and forty-four

805-MHz Coupled Cavity Linacs (CCLs). As a part of

the upcoming LANSCE Modernization project, low-level

RF (LLRF) systems of four 201-MHz DTLs and twenty-

six 805-MHz SCLs have been digitized. Hence the net-

work-based control of the cavity field and RF commis-

sioning are possible. Each LLRF and high-power RF

(HPRF) systems have many process variables (PVs) lo-

cated on different computer control screens provided by

the Extensible Display Manager (EDM). Several

MATLAB m-scripts have been developed to efficiently

process the necessary PVs while auto-start, ampli-

tude/phase calibration, gain tuning of the cavity field

feedback controllers, gain and phase tuning of the beam

feedforward controllers, and high power RF trip recovery,

processes are configured and validated. This paper ad-

dresses the sequence of RF commissioning of the

LANSCE LINAC from the time of RF-turn-on to beam

feedforward control and its relevant EDMs and MATLAB

m-scripts.

1. INTRODUCTION

The LANSCE LINAC is composed of one 201.25

MHz Drift-Tube_Linac (DTL) sector and seven

805MHz Coupled-Cavity Linac(CCL) sectors. A 805

MHz sector is composed of 6~7 CCLs with one high

voltage system, Capacity Bank. In contrast, the 201.25

MHz sector is composed of 4 DTLs and each DTL has its

own high voltage system [1]. The LLRF systems of four

DTLs and twenty-six CCLs were digitized in the last sev-

eral years.

Since these digital LLRF (DLLRF) systems work in

the baseband frequency domain, the structure of the

LLRF control system are the same and the digital signal

processing (DSP) – downconversion to the baseband sig-

nals, filtering, control signal generation, upconversion to

the IF signals − that are implemented on the Intel FPGA

are very similar. Figure 1 shows the overall LLRF control

system block diagram. In figure 1, all submodules such

as the RF upconverter, intermediate power amplifier and

high power amplifier, on the RF drive path are represent-

ed as the lumped transfer function 𝐻𝑓𝑤𝑑(𝑠) and all sub-

modules such as RF pickup, RF downconverter, IF filter,

on the RF feedback path is represented as the lumped

transfer function 𝐻𝑟𝑒𝑡(𝑠) [2].

Because the digitization was accompanied with the

LANSCE Control System (LCS) network support, the

network based control of the LLRF control system be-

came possible. Control parameters of LLRF system are

assigned with parameter variables (PVs) of the EPICS

Database and the operation of the (LL)RF system can be

performed by adjusting those PVs properly. In addition,

since the measured signals of the LLRF control system

are transmitted to the LCS network, it is possible to im-

plement data based digital signal processing on the host

system connected to the LCS network.

MATLAB is used widely at LANSCE for sig-

nal/image analysis and synthesis of LLRF digital signal

processing (DSP). MATLAB is also used for controlling

PVs of (LL)RF system. For this, a compact MATLAB

version of EPICS channel access (CA) was developed,

where MATLAB m-script uses Operating System (OS)

function “system” to call EPICS CA functions, caget,

caput, etc..

The procedure of the RF operation and Beam operation

is comprised of (i) turn on RF and adjust amplitude and

phase set points of the cavity field to the pre-assigned

target values; (ii) calibrate the open loop gain and phase;

(iii) close the PI feedback loop and calibrate the cavity

amplitude and the cavity phase of the external measure-

ments to the stored target values; (iv) tune the beam feed-

forward controller. Automations of (i), (iii), (iv) are ac-

companied with callings of MATLAB functions.

Figure 1. LLRF Control System Block Diagram

2. RF TURN ON FOR START UP OR

VSWR RECOVERY

RF turn on and adjustments of amplitude and phase

set points are performed either for the first start up of the

LINAC RF operation or for the RF Trip Recovery. Target

amplitude and phase set points are retrieved from an au-

________________________________________

* Work supported by U.S. Dept. of Energy

† email address: skwon@lanl.gov.

+Cavity

Controller

Feedforward

Controller

Disturbance

Observer

Beam Current

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MATLABScriptsforRFCommissioningattheLANSCELINAC*SungilKwon†,A.Archuleta,L.Castellano,C.Marchwinski,M.Prokop,P.VanRooy,P.TorrezLosAlamosNationalLaboratory,LosAlamos,NM,USAAbstractThelinearaccelerator(LINAC)attheLosAlamosNeu-tronScienceCenter(LANSCE)consistsofPre-buncher,Main-Buncher,low-energybeamtra...

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MATLAB Scripts for RF Commissioning at the LANSCE LINAC Sungil Kwon A. Archuleta L. Castellano C. Marchwinski M. Prokop P. Van Rooy P. Torrez Los Alamos National Laboratory Los Alamos NM USA.pdf

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MATLAB Scripts for RF Commissioning at the LANSCE LINAC Sungil Kwon A. Archuleta L. Castellano C. Marchwinski M. Prokop P. Van Rooy P. Torrez Los Alamos National Laboratory Los Alamos NM USA

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