Overview and first Simulation Results Lutz Matthias Hein 1 General - - PowerPoint PPT Presentation

CLIC - Decelerator

Overview and first Simulation Results

Lutz Matthias Hein 1

General Overview

Lutz Matthias Hein 2

12 GHz RF-System

Why 12 GHz?

Lutz Matthias Hein 3

CLIC

100..120 MV/m 12 GHz

Tesla Cavities

50..60 MV/m (supercond.) 1[..]3 GHz ~ 35MV/m

Frequency [MHz] Electric Field [MV/m]

Why 4 Beams?

• Normal Conducting Material - Copper

Lutz Matthias Hein 4

CLIC

100..120 MV/m

Tesla Cavities

50..60 MV/m (supercond.)

12 GHz – Drive Beam

Lutz Matthias Hein 5

CR2

CR1

DL

x2 x3 x4 x24

Drive Beam Linac

RF 1 GHz with 0.5 GHz Bunch Structure 12 GHz Bunch Structure

100 × ‘safe beam’

6.14GeV 1500GeV Stronger quadrupoles required

• > Skip cavities for quadrupoles
• > 24 different Decelerator Lattices

Types of Decelerator

6

(830m) (1040m)

Important to know !!

Lutz Matthias Hein 7

The Decelerator is used to decelerate the Drive Beam!

1 2 3 N N-1

The head sees an empty cavity meanwhile the rest experiences the beam wake fields.

• > Hugh Energy Spread

Main Objectives

• Detect and estimate particle losses
• Investigate the LOSS PATTERNS
• Find Damage Limits

Lutz Matthias Hein 8

Possible Errors

• Misinjection
• Quadrupole Alignment
• Quadrupole Field Errors

(assumed to be static during 1 bunch train)

• RF-Break-Downs -> Wrong Energy, Dipole Kick ...
• ???

Lutz Matthias Hein 9

• Misinjection
• Quadrupole Alignment
• Quadrupole Field Errors

(assumed to be static during 1 bunch train)

• RF-Break-Downs -> Wrong Energy, Dipole Kick ...
• ???

Possible Errors

Lutz Matthias Hein 10

Used to simulate

Step 1

Lutz Matthias Hein 11

Estimate Limits of Single Quadrupole Offsets

Decelerator Nr. 11 (with 876 Quadrupoles):

1 2 3 876 875 1 2 3 876 875

Misalign single Quadrupole:

!! There are differences between focusing and defocusing Quadrupoles !!

(spq ≈ 20µm)

Physics – Wakefields

Lutz Matthias Hein 12

Alignment Error -> Beam Offset

F D

2 3

Wakefields in the Beam Pipe

Beam Pipe Real Beam Image Charge Image Charge

Physics – Wakefields

Lutz Matthias Hein 13

Dipole Modes and Beam Break-Up

Due to the bunch offset dipole modes of the cavity are excitated, which stimulate the following bunches to enhance these modes.

Physics – Wakefields

Lutz Matthias Hein 14

Dipole Modes and Beam Break-Up

At certain configurations of beam current, cavity quality etc. the dipole modes can ‚kick-out‘ the beam, so call Beam-Break-Up.

Results of the Energy Spread

Lutz Matthias Hein 15

F

Low Energy High Energy I) Kick itself II) Chromaticity

F

Focus High Energy Low Energy

• > Filamentation &

Emittance Growth

G – Space Q(51)

Lutz Matthias Hein 16

50µm 100µm 200µm 500µm 750µm 1000µm

X [µm] X‘ [µrad]

Most Important Parameter

Lutz Matthias Hein 17

Charge Density:

Scraping !! I= Q Dx*Dy

X [µm] X‘ [µrad]

Characteristic Curves

Lutz Matthias Hein 18

Quadrupole Offset [µm] Xmax [µm]

When do we hit the aperture?

Damage Levels

Lutz Matthias Hein 19 Quadrupole Offset [µm] Xmax [µm]

How does the Beam look like?

I = Q Dx*Dy Above Damage Level ??

Map of the max. Beam Kicks as Function of the Damage Level

X Y

Step 2

Lutz Matthias Hein 20

Estimate Limits of Multiple Quadrupole Offsets

Decelerator Nr. 11 (with 876 Quadrupoles):

1 2 3 876 875 1 2 3 876 875

Misalign of several Quadrupoles:

• When can I simply add qp-kick up?
• When do the kicks amplify the emittance?

Drawbacks

Lutz Matthias Hein 21

In the decelerator particle tracking is not possible. Tracking is done with a special beam consisting of macro-particle + S-matrix Xj Xi post-processing needed for Intensity distribution Particle Losses Damage Evaluation Sliced Beam

+

Pre-/Post-Processing

Lutz Matthias Hein 22

Own Code for Post Processing

• 1. Intensity Calculation

X Y

• 2. Loss Detection

Satellite Particles

• 3. Energy Deposition

In Progress

Drawbacks

Lutz Matthias Hein 23

Electron Beam:

• 2.4 GeV down to 200MeV
• 12 GHz Structure -> 1mm .. 6 mm Beam length
• 8.4 nC bunch charge

Space Charge Effects are not included in the simulation code so far.

? Space Charge Effects ?

Try other Programms to estimate space charge effects

• > Particle Distribution and Lattice are needed to be converted.

Drawbacks

Lutz Matthias Hein 24

Use other program to estimate the space charge effects Path Manager + tested and benchmarked for Hadron Linacs + easy to use and free output data + Particle tracking + good manual

• no detailed tests for

electron linacs

• no wake fields

Astra + tested and benchmarked for Electron linacs incl. gun + “easy“ to use and output data + good manual + Particle tracking

• Need Field maps for the

PETS

Space Charge Results

Lutz Matthias Hein 25

First results: Placet Vs. Path Manager (no Space Charge)

Space Charge Results

Lutz Matthias Hein 26

First results: Path Manager (Space Charge)

Outlook

Lutz Matthias Hein 27

• Perform Space Charge Calulations using ASTRA
• Get lost patterns for single Quadrupole kicks
• check filamentation
• damage levels / damage as Fct.(s)
• Quadrupole Kicks Step 2