Linac Upgrade:

Beam Instrumentation( Nondestructive Beam-Energy-SpreadMonitor System )M. Satoh, T. Suwada and K. Furukawa(KEKB Linac Control/Commissioning Group)

M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

= Contents =1. Motivation
2. Nondestructive Energy-Spread Monitor
3. Fast DAQ System
4. Results of Data Analysis
5. Summary & Future Plan

M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

= Motivation =• Beam feedback controls of the KEKB injector linac
are very important for stable beam operation:– Beam position feedback (works)– Beam energy feedback (works)– Beam energy-spread feedback (under construction)

Nondestructive Beam-energy-spread monitor isstrongly required !!
M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

= Energy-Spread Monitor =Screen Monitor (@ηx≠ 0)• Energy spread can bemeasured by using Fluorescent
Screen-Monitor.
• “Eye Measurement”• ”Destructive” beam monitor(Not desired).

• Quantitative measurement• Nondestructive monitor isneeded.
M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

Energy-Spread Monitor using BPM
Strip line-type BPM with eightelectrodes is used as :• Nondestructive Energyspread monitor(Measurement of Quadrupolemoment Jq)• Quantitative measurementθ ≠ 0, π
8Vi cos 2θ
∑122Jq = 2 x 2 − y 2 + x − y ≅ i =1 8R∑Vi()i =1• SR may hit the electrodes.

3π 5π 7πθ≠ ,,,4 4 4 4π

2x2 − y2

 ΔE ≅ η x + β xε x − β y ε y + gE 
M. SATOH/ KEKB Linac Control• Quadrupole moment term willvanish.

KEKB Review Committee, Feb. 16-17, 2004

Beam Energy-Spread Monitor with Eight Stripline Electrodes (@ηx≈ 0.72 m)

M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

= DAQ System =Software
PC (Linux)

Python / Tkinter (GUI)(Oscilloscope,Data processing

C++/Linux / OS

• It consists of only twoparts. (Oscilloscopeand PC)

Linac Control Network

Oscilloscope• Simple system setup
can enhance thesystem reliability.

DAQ System
Energy Spread Monitor (ESM)
M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

Trend plot Software

M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

DAQ rate
150DAQ rate [Hz]50Hz1005000200400600• Two bunch operation,
signal width 〜 500 ns
Max.
(interval : 96 ns)
Min
Average• Oscilloscope can obtaina waveform data up to50 Hz.
• Each bunch (1st and 2ndbunch) data can be
simultaneously
obtained.
800
1000

Signal length [ns]M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

Pulse-to-Pulse Measurementin 50 Hz mode
Horizontal position [mm]Vertical position [mm]
Energy spread [a.u.]

10 nC

2128614200

Energy spread [a.u.]

Beam position [mm]10-2020406080-4100

Pulse No.
M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

= Results of Data Analysis =2 weeks

1st bunch
2nd bunch

2004/1/23 - 2/9

18
14
12
1086

2

2

2

<x > - <y > [mm ]16420-21/23

1/24

1/25

1/26

1/27

1/28

1/29

1/30

1/31

2/1

2/2

2/3

2/4

2/5

2/6

2/7

2/8

2/9

date [mm/dd]

1 week

1st bunch
2nd bunch

2004/1/23 - 1/30

18222

<x > - <y > [mm ]1614121086420-21/23

1/24

1/25

1/26

1/27

1/28

1/29

date [mm/dd]

M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

1/30

1 day Fluctuation of Energy-Spread
14222<x > - <y > [mm ]12

1st bunch
2nd bunch

2004/2/3

10864
20-2

2004/02/03 00:00

2004/02/03 08:00

2004/02/03 16:00

2004/02/04 00:00

date [mm/dd]
M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

222

1st bunch <x > - <y > [mm ]Energy-Spread Fluctuation(1st vs. 2nd bunch)1211109876543210-1-2-3-4-2• The 2nd bunch energy
spread is about twice
larger than that of 1stbunch.
• Each bunch may be
accelerated on thedifferent phase of Sband RF.

81602468102122141618

2

2nd bunch <x > - <y > [mm ]M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

2nd Bunch Position and Chargevs. Energy-Spread trend54

2nd bunchx position
charge04/1/22-2/91083x [mm]610-1AB-22-3-4-6 -4 -2 04246208 10 12 14 16 18 20 22
2charge [nC]2

• As the energyspread increase,beam charge
decrease linearly.
• The inclination
changes at energy
spread “6” (A andB).

2<x > - <y > [mm ]M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

2nd Bunch Position and Charge
vs. Energy-Spread trend (contʼd)
Beam duct•xxnominal•xBA

M. SATOH/ KEKB Linac Control•

As the energy spreadincreases, the horizontal
position move toward left.
Above the energy
spread “B”, horizontal
position is almost
constant.
Beam tail will be cut by
the beam duct.

KEKB Review Committee, Feb. 16-17, 2004

Energy-Spread Fluctuation
ratio of 2nd to 1st bunch60

2003 Nov.
2004 Jan.22-Feb.9 (CIM)

40

Inphase line

220
0

2

<x > - <y > ratio of 2nd to 1st bunch

80

-20

05000

10000

15000

20000

25000

• “Inphase line” :1st and 2nd bunch energy
spread varies almost
inphase.
• As the displacementfrom this line increases:
Energy spreadfluctuation of eachbunchdata number(*) CIM: Continuous injection mode
M. SATOH/ KEKB Linac Control

independent.
KEKB Review Committee, Feb. 16-17, 2004

FFT Analysis of energy spreadfluctuation ratio (2nd/1st)•1.0

2003 Nov.
2004 Jan.22-Feb.9 (CIM)

0.9

Intensity [a.u.]

0.80.7

Result of FFT is different
between Continuous Injection
Mode (CIM) and previous
operation mode (Injection was
carried out in every hour.)

0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.00

0.02

0.04

0.06

0.08

0.10

Frequency [Hz]M. SATOH/ KEKB Linac Control

KEKB Review Committee, Feb. 16-17, 2004

Summary & Future Plan
• Nondestructive Energy-Spread Monitor (Quantitativemeasurement) and fast DAQ system were developed
for the Energy-Spread Feedback System.
• It works well in the daily operation.
• The fluctuation of 2nd bunch energy spread is larger thanthat of 1st bunch (approximately double).
• More detailed data analysis is needed.
• The Energy-Spread Feedback System will be tested in thenear future.

M. SATOH/ KEKB Linac ControlKEKB Review Committee, Feb. 16-17, 2004