OPTIMIZATION OF RF PHASE AND BEAM LOADING DISTRIBUTION AMONG RF STATIONS IN SuperKEKB S. Ogasawara K. Akai T. Kobayashi K. Nakanishi M. Nishiwaki

2025-04-29 0 0 1.01MB 5 页 10玖币

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OPTIMIZATION OF RF PHASE AND BEAM LOADING DISTRIBUTION

AMONG RF STATIONS IN SuperKEKB

S. Ogasawara†, K. Akai, T. Kobayashi, K. Nakanishi, M. Nishiwaki,

High Energy Accelerator Research Organization (KEK), Tsukuba, Japan

Abstract

SuperKEKB is the e-/e+ collider which targets the world

highest luminosity. In recent operation, SuperKEKB

achieved a new world record of   for

luminosity with the beam current of 1.4 A. In the future,

the beam current will be increased further to aim at the de-

sign value of 3.6 A and much higher luminosity. The RF

system consists of 38 cavities (30 klystron stations), which

share the huge beam loading brought by high current beam

with each other cavities. For beam stability and power ef-

ficiency, it is important to distribute the beam loading

properly among RF cavities. It is equivalent to adjust the

acceleration phase of each cavity. However, it is difficult to

evaluate the acceleration phase using only the pickup sig-

nal. Therefore, we established a method to evaluate the

beam loading balance among RF stations from the RF

power measurement for each cavity, and to adjust the ac-

celeration phase. This report introduces the method for

evaluating and optimizing the beam loading (acceleration

phase) among stations in SuperKEKB, which has a large

number of RF stations, and its operation.

OVERVIEW

SuperKEKB is an e-/e+ collider upgraded from KEKB,

which targets the world highest luminosity [1]. In recent

operation, we achieved a new world record luminosity with

the beam current of 1.4 A [2]. SuperKEKB consists of two

rings, 7-GeV electron ring (High Energy Ring, HER) and

4-GeV positron ring (Low Energy Ring, LER). To achieve

higher luminosity, the beam current is designed as a large

value, 3.6 A (LER). Due to the huge beam current, the huge

RF power (beam loading) is required.

The RF system consists of two-types 38 cavities in two

rings [3,4]. The number of RF (klystron) stations is 30 with

three types of station. In order to accumulate the high cur-

rent beam stably and efficiently, it is important to optimize

the beam loading balance among RF stations with consid-

ering the difference of station types. The optimization of

the beam loading corresponds to adjust the station phase.

This paper introduces a method for evaluating and opti-

mizing the beam loading among the RF stations in

SuperKEKB.

THE RF SYSTEM

Table 1 shows RF-related operation parameters. Figure

1 shows an arrangement of RF stations in SuperKEKB

rings. There are three acceleration (RF) sections at each

ring (total six sections for the two rings). The RF frequency

is 508.9 MHz

Table 1: Operation Parameters of RF System. [3-5]

*: design value

Figure 1: Arrangement of RF stations in SuperKEKB

SuperKEKB has two types of cavities: normal conduct-

ing “ARES” cavity and superconducting cavity (SCC) [6].

ARES cavity is a unique cavity system specialized for

KEKB [7]. SCC is applied to only HER. HER has eight

ARES cavities and eight SCCs. LER has 22 ARES cavities.

The RF system has three station types of “ARES-1:1”,

“ARES-1:2” and “SCC”. ARES-1:1 means that one klys-

tron (KLY) [8] drives one ARES cavity, and ARES-1:2

means that one KLY drives two cavities. SCC station has

one cavity driven by one KLY. For the design of

SuperKEKB, the 1:1 configuration will be applied to all

ARES stations in HER. However, the present state is at the

halfway stage of the upgrade for the design.

LER

HER

Beam Energy [GeV]

4.0

7.0

Beam Current [A]

3.6*

2.6*

Loss Energy [MeV/turn]

1.76

2.43

Cavity Type

ARES

SCC/ARES

RF Frequency [MHz]

508.9

# of Cavities (# of Stations)

22 (16)

8(8)/8(6)

RF Peak Voltage

[MV/cavity]

0.5*

1.5*/0.5*

Beam Power [kW/cavity]

400~*

400*/600*

Klystron Power

[kW/station]

~800*

~450*/800*

___________________________________________

† shunto.ogasawara@kek.jp

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OPTIMIZATIONOFRFPHASEANDBEAMLOADINGDISTRIBUTIONAMONGRFSTATIONSINSuperKEKBS.Ogasawara†,K.Akai,T.Kobayashi,K.Nakanishi,M.Nishiwaki,HighEnergyAcceleratorResearchOrganization(KEK),Tsukuba,JapanAbstractSuperKEKBisthee-/e+colliderwhichtargetstheworldhighestluminosity.Inrecentoperation,SuperKEKBachievedane...

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OPTIMIZATION OF RF PHASE AND BEAM LOADING DISTRIBUTION AMONG RF STATIONS IN SuperKEKB S. Ogasawara K. Akai T. Kobayashi K. Nakanishi M. Nishiwaki

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