The MERLIN Simulations Program: New features used in studies of the LHC Collimation System

unkindnesskindΠολεοδομικά Έργα

15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

60 εμφανίσεις

THP101

The MERLIN Simulations Program: New features
used in studies of the LHC Collimation System

R.J. Barlow, R. Appleby, J. Molson, H.L. Owen, A. M. Toader


www.cockcroft.ac.uk


www.manchester.ac.uk

The

collimation

system

of

the

LHC

will

be

critical

to

its

success,

as

the

halo

of

high

energy

(
7

TeV
)

particles

must

be

removed

in

such

a

way

that

they

do

not

deposit

energy

in

the

superconducting

magnets

which

would

quench

them,

or

showers

in

the

experiments
.

We

study

the

properties

of

the

LHC

collimation

system

as

predicted

by

the

Merlin

and

Sixtrack/K
2

simulation

packages,

and

compare

their

predictions

for

efficiency

and

halo

production,

and

the

pattern

of

beam

losses
.

The

sophisticated

system

includes

many

collimators,

serving

different

purposes
.

Both

programs

include

energy

loss

and

multiple

Coulomb

scattering

as

well

as

losses

through

nuclear

scattering
.

The

MERLIN

code

also

includes

the

effects

of

wakefields
.

We

compare

the

results

and

draw

conclusions

on

the

performance

that

can

be

achieved
.



Acknowledgements
:


We

like

to

thank

Prof
.

Sandy

Donnachie

for

providing

us

with

theoretical

framework


of

the

Pomeron

exchange

implemented

in

MERLIN
.


Particle Loss Maps

Collimator Scattering Process:
Pomeron

exchange

Introduction




M

ERLIN

is

a

particle

tracking

code

that

we

have

enhanced

to

be

able

to

take

advantage

of

multicore

CPUs

and

computer

clusters
.

This

gives

a

manyfold

increase

in

speed,

tracking

millions

of

particles

element

by

element

over

hundred

of

turns
.


The

LHC

Collimators

are

designed

to

remove

halo

particles

so

that

they

do

not

impinge

onto

either

detectors

or

other

vulnerable

regions

of

the

storage

ring
.


It

is

crucial

to

model

them

accurately,

including

the

simulation

of

protons

scattering

at

very

small

t
,

which

can

survive

several

turns

before

being

lost
.

The

physics

of

such

soft

processes

at

high

energies

are

well

described

by

recent

Pomeron

exchange

models,

which

describe

the

data

from

ISR

to

Tevatron

energies
.

This

is

the

relevant

region

for

the

LHC,

where

the

protons

involved

collide

with

a

fix

target

at

\
sqrt(s
)=

81
GeV

and

118
GeV

for

3
.
5

and

7

TeV

beams
.


We

incorporate

the

elastic

and

quasi
-
elastic

diffractive

cross

sections


for

low

momentum

transfer

(
0
.
0001
<
t
<
0
.
01
GeV
2
)

into

tracking

code

MERLIN,

and

use

it

to

simulate

the

maps

of

the

beam

halo

lost

in

the

collimators
.

The

scattering

routines

track

the

protons

through

some

length

of

a

given

material

having

them

interacting

with

the

proper

cross
-
sections
.




Top left:
xy

real space bunch distribution through a tilted collimator.

Top right:
x

&
y

phase space after the collimator showing the scattered particles.

Bottom left and right: TWISS parameters at the collimator



Snapshot of Particle Tracking with MERLIN around the LHC ring