energy deposition studies at ir7

Energy deposition studies at IR7

M. Santana, M. Magistris, A. Ferrari, V. Vlachoudis

Collimation collaborationmeeting 09-05-2005

Introduction

Motivation

Large Hadron Collider : 27 km cryogenic installationLarge Hadron Collider : 27 km cryogenic installation

LHC is a proton-proton colliderLHC is a proton-proton collider 2 proton beams at 7 TeV of 32 proton beams at 7 TeV of 3××101014 14 pp++ each each stored for 10-20 hours in collisionstored for 10-20 hours in collision total stored energy of 0.7 GJ (sufficient total stored energy of 0.7 GJ (sufficient to melt 1 ton of Cu)to melt 1 ton of Cu)

~5000 cold magnets~5000 cold magnets Tiny fractions of the stored beam suffice to quench a Tiny fractions of the stored beam suffice to quench a

superconducting LHC magnet or even to destroy parts superconducting LHC magnet or even to destroy parts of the accelerators.of the accelerators.

The LHC collimation system will protect the accelerator The LHC collimation system will protect the accelerator against unavoidable regular and irregular beam loss. against unavoidable regular and irregular beam loss.

from MC2005 V. Vlachoudis

Two Stage Cleaning

Secondary halo

p

pe

Pri

mar

yco

llim

ator

CoreCore

Diffusionprocesses1 nm/turn

Shower

Beam propagation

Impact parameter

≤ 1 m

Sensitive equipment

Primary Primary halo (p)halo (p)

e

Shower

p

Tertiary halo

Secondary collimator

79.54.54Titanium

96.41.77Graphite

34.48.96Copper

971.848Beryllium

88.82.7Aluminum

Escaping

%

Density g/cm3

Material

Example for 1 m long jaws!

Secondary collimators intercept halo --> Shower energy escapes Secondary collimators intercept halo --> Shower energy escapes to downstream elements! so then... to downstream elements! so then... What happens downstream?What happens downstream?

RADWG-RADMON Workshop Day, CERN 01/12/2004 5

E6C6

IP7A6

A6C6E6

UJ76

RR77

RR73

IR7 layout

LHC lattice and optics files V6.5

1. Primary and Secondary collimators, Scrapers, Absorbers

Normal operation 0.2 hours beam lifetime 4×1011 p/s for 10 s

RADWG-RADMON Workshop Day, CERN 01/12/2004

6

IR7 Geometry

UJ76

RR73 RR77

Geometry of the dipoles

Tesl

a

14m long objects with a field of 8.3 Tesla: 5mrad bend ~3cm sagitta.The superconducting dipoles(MB)are made out of 4 straight sections to accommodate the trajectory.

Magnetic field maps

● General routine for handling magnetic field maps (Analytic and/or 2D Interpolated) with the use of an external file with a special format

● Magnetic field type– CONSTConstant field– QUAD 2D Analytic quadrupole field– QUADINT 2D Analytic+Interpolated quadrupole field– INTER2D 2D Interpolated field

● Symmetries:– NONE No symmetry– X, Y, Z Symmetrical on plane X, Y, Z (-x x, …)– XY On both planes XY– XYZ On all planes XYZ

● Table with interpolated data (Bx,By,Bz)● Quadrupole analytic description

– Origin of the magnetic field map origin– Limiting radius up to where to consider an analytic field

● Translation and Rotation of the field map● Field intensity / gradient specified per region or lattice


Magnetic field example

MQW – Warm Quadrupole

XY SymmetryAnalytic

2D Interpolated


Primary Inelastic collisions map

● Generated by the COLLTRACK V5.4 program– 3 scenarios: Vertical, Horizontal and Skew– Pencil beam of 7 TeV low-beta beam on primary collimators– 100 turns without diffusion– Impact parameter: 0.0025 – Spread in the non-collimator plane: 200 m– Recording the position and direction of the inelastic interactions

● FLUKA source: Force an inelastic interactions on the previously recorded positions

Beam Loss Map

M. Brugger et al


Execution timeBiasing● Importance biasing: radially decreasing● Leading particles biasing● High energy cuts on EMF on regions far away● Weight Windows per region

Statistics● 30% on maximum● Linux Cluster● 64 CPU’s @ 3GHz● 1 week run

Improvements:● Bias the diffractive/inelastic

scattering ratiofrom MC2005 V. Vlachoudis

Collimators

Collimators Material ChoiceNot driven so much by the standard collimationbut rather by the faulty operations or malfunctions● Worst Accident scenarios:

– Due to a spontaneous rise of one of the extraction kicker modules during the coast, part of the 7 TeV/c beam is spread across the front of a collimator jaw.

– Faulty kick by the injection kicker where a full batch of protons hit the front of a collimator jaw at 450 GeV/c

● Very fast absorptions of part of the proton energy:

– Instantaneous temperature rise– Thermally induced stresses (overheating/melting)

Limits material choice which can be used and still be compatible with other machine requirements.

● FLUKA-2002-4 A.Fasso, A.Ferrari, J.Ranft, P.R.Sala Proceedings of the Monte Carlo 2000 Conference, Lisbon, Oct. 23-26 2000, Springer-Verlag Berlin, p 955-960 (2001)


Collimators

Criteria:● Primary and secondary collimators

are the closest elements to the beam● Activating single scattering for thin

layer on jaws● Jaw halfgap / tilt variable during

runtime Primaries:

Gap: 6 Jaws: C-CLength: 20cm... may be changed to 60

Secondaries:Gap: 7 Jaws: C-CLength: 100cm

Absorbers:Gap: 10 Jaws: Cu or WLength: 100cm


Secondary Collimator

Maximum Energy density in TCSGA6L1 carbon jaws

Simulations

Simulation Strategy● Dynamic FLUKA input generation with several ad-hoc scripts● Detailed description of 20 prototypes located in a virtual parking zone.● Prototypes are replicated with the LATTICE card, rotated and translated.● Magnetic field maps: Analytic + 2D Interpolated● Dynamic generation of the ARC (curved section)● Optics test: Tracking up to 5 , both vertical / horizontal, reproduce beta

function

Input FilesInput Files• FLUKA input template• Twiss files• Collimator summary• Absorbers summary• Prototype Info

mklattic.rBRexx Script

Fluka Input Fluka Input (.inp)(.inp)

• LATTICE definitions• Curved Tunnel creation• Magnetic Fields Intensity• Scoring cards

Fluka Fluka ExecutableExecutable

• LATTICE transformations• Dynamic adjustment of

collimator gaps

Fortran FilesFortran Files• Source routine• Si Damage 1 MeV n eq.• Magnetic Field• History Tracking

Automatic Geometry Creation

1. Initial input file template2. Space Allocation & Geometry Creation3. Lattice generation4. Magnetic Fields mapping

Implementation of vertical and horizontal absorbers

Beam profile

z(m)

Geometry

Like secondary collimator, with Cu jaws and10 sigma halfwidth

Steps to launch a simulation

● 1) Modify active absorbers:

#icoll Name Material Length Rotation Tilt(jaw1) Tilt(jaw2) Halfgap N_Impacts N_InelInt Impact(av) Impact(sig)# [m] [rad] [rad] [rad] [m] (protons) (protons) [m] [m] 1 TCL.A4R7.B1 CU 0.000 0.1571000E+01 0.000000E+01 -0.1669557E-04 0.3517000E-02 267759 120004 0.8801409E-05 0.2861191E-04# 1 TCL.A4R7.B1 CU 0.000 0.0000000E+01 0.0000000E+01 -0.1669557E-04 0.1931000E-02 267759 120004 0.8801409E-05 0.2861191E-04# 1 TCL.A6R7.B1 CU 1.000 0.1571000E+01 0.0000000E+01 -0.1669557E-04 0.1585000E-02 267759 120004 0.8801409E-05 0.2861191E-04# 1 TCL.A6R7.B1 CU 0.000 0.0000000E+01 0.0000000E+01 -0.1669557E-04 0.3859000E-02 267759 120004 0.8801409E-05 0.2861191E-04...

twiss/absorber_summary.dat

"RCOLLIMATOR" "TCL.A4R7.B1" 0 0 20022.5326 0.00 0.00 0.00 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 "RCOLLIMATOR" "TCL.A6R7.B1" 0 0 20148.3344 0.00 0.00 0.00 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Absoluteposition

V6.5_absorbers.b1.phase1.data

Use twiss/tensigma.dat

1.000 = active0.000 = inactive # = no line

0.1571 = Vertical0.0000 = Horiz.

- Each absorber must be defined in both files (inactive absorbers count but not hashed lines).- There cannot be two active replica of the same absorber.

Steps to launch a simulation

● 2) Modify geometry, activate relevant USRBIN in ir7.fluka

– USRBIN -39.0 must always be active.● 3) Check for errors in prototypes etc.:

– $ fluka.r -m ir7.fluka ir7.i– $ mcnpx ip i=ir7.i

● 4) Select appropiate beam file:– Check ir7.fluka:

– Check run.sh to include that beam:

BEAM 7000.0 PROTONSOURCE beam1*SOURCE A7*SOURCE B7

ir7.fluka

SOURCES="Twiss/beam1.dat Twiss/beam2.dat Twiss/beam1V.dat Twiss/beam1H.dat Twiss/beam1S.dat Twiss/beam1VP.dat Twiss/beam1VPH.dat Twiss/beam1VPS.dat Twiss/beam1VPV.dat Twiss/beam1VS1.dat Twiss/A7.dat Twiss/B7.dat Twiss/nbeam1.dat"

run.sh

Steps to launch a simulation● 5) IF a new prototype has been designed, include it in prototype.pos:

● 6) Compile geometry --> ir7.inp:– $ make proper– $ make

● 7) Check correctness of ir7.inp:– Check number and type of absorbers ir7.inp.– Make plots of newly introduced elements:

● $ flukaplot.r ir7.inp flukair7● 8) Make a test run:

– Check results and speed.– Check lattice tables:

● $ EnLattice.pl < 'ir7.inp' 'usrbinf_39' '1'● 9) RUN and analyze.

prototype.pos

# Absorber (like Hybrid)TCL 0 0 TCL2 -2000.0 0.0 5060.0 100.0 -#

One or two beams(normalization)

File with formatted results $ usbsuw to summarize $ usbfuf to format

1 or 2 beams

Correction of beam direction.

x

x

z

yOnly primaries are affected

85% inelastic scattering(minor consequences)

15% diffractive scattering(deviated and partially

lost)

40% more dose in MQTLH,

but still below limit

Much higher dose in the curved section,but still well below the limit

0.5 mrad rotation

Mq6totMQ7

MBA8R

MBB8R MQ8

MBA9R

MBB9R MQ9

MBA10R

MBA11R

MBB11R MQ11

MBA12R

MBB12R 0

2

4

6

8

10

12

14

16

18

20

22

24Dose increase for correct beam

Dose

corr

ect

/ u

nco

rrect

beam

Results:warm elements

Preliminary results for the straight section (corrected beam)

Total energy deposited in the MBWB6L:Corrected beam: 28.4 kW

(Uncorrected beam: 37 kW)

Energy deposited in the TCSGA6L1:Total energy: 20 kW

(Uncorrected beam: 22.6 kW )Energy in both jaws: 5.1 kW

(Uncorrected beam: 1.02 kW )

Hot spot with no physical meaning, due to the beam error

Heat in the finger collar of the TCSGA6L1

16.9 W 80.4 W

Energy deposition in flanges

W/cm3

TCSGA6L1

<-front

back->

70 W

22 W

457 W

85 W

Passive absorber

● Most of the radiation deposited in the MBW insulator comes from inside the beam pipe.

● The efficiency of the absorber strongly depends on the inner radius.Ideal absorber. Pipe size. Fe absorber. 2 cm radius (pipe

is 4 cm)

5-10 MGy/y ~ 1 MGy/y

● Need for smaller radius. Cu absorber? Ideas?

Results: cold elements

Implementation of vertical and horizontal absorbers

1 Finally selected.

TCL.A6R7.B1s= 20148.33

TCL.C6R7.B1s= 20179.29

TCL.E6R7.B1s= 20213

6 candidate absorbers in straight section

2 candidate absorbers before curved section

4 Finally selected

TCL.B7R7.B1s= 20236.65

Beam 1

Beam 2

TCL.A7R7.B1s= 20251.65

TCL.A4R7.B1

TCL.F6R7.B1

Radiation in the MBA8

Heat spikes in MB's

Radiation in the MQ's

1W +- 0.5 W 1W +- 0.5 W 0.01W +- 0.01 W

mW

/cm

3

Comparison between A7h and B7h

Part of the beam halo will interact with the absorbers and generate a hadronic shower => energy deposition in the cold

magnets

The contribution from B7h will be 15% higher than A7h, but still at an acceptable level.

Peak values in MQ7:

A7h => 0.22 mW/cmc (*) B7h => 0.26 mW/cmc (*)

(*) values refer to 1 proton interacting out of 10,000 lost in TCP. Error is below 6%.

MQ7 MBA8R MBB8R MQ8 MBA9R 0.1

1

10

100

1000

10000

Energy deposition in coils (W), total beam lost in the last absorber

A7h

B7h

Po

we

r (W

)

Tertiary halo

Comparison between A7h and B7h

● Simulations were run with corrected beam.● The accuracy of the magnetic field in the MB was improved.

● Low energy photons were fully simulated.

from PAC2005 M. Santana et al.

Comments

Simulation accuracy. Sources of error

- Physics modeling:– Uncertainty in the inelastic p-A extrapolation cross section at 7 TeV lab

– Uncertainty in the modeling usedFactor ~1.3 on integral quantities like energy deposition (peak included)while for multi differential quantities the uncertainty can be much worse.

- Layout and geometry assumptions: It is difficult to quantify, experience has shown that a factor of 2 can be a safe limit.

- Beam grazing at small angles on the surface of the collimators: Including that the surface roughness is not taken into account a factor of 2 can be a safe choice.

- Safety factor from the tracking program COLLTRACK is not included!


Some facts ...

- Challenge:– 'Filter twice 450 kJ' in such a way that superconducting elements get less than 5 mW/cm3!

– Track showers along 1.5 km of tunnel and build up statistics with rare occurring events.

- Resources: Over 7 years of equivalent CPU-(2.8 GHz) over 15 months in a 3 man-year effort.

- Models and scripts: one of the most complex simulations in FLUKA.

Related works:UJ & RR's

electronicsprotection

K. Tsoulou


41

NoAbsorbers

A6vC6Eh6v Absorbers

RR77RR73

Dose

(G

y/y

)

UJ76

Flux (

cm-2/y

)

A6vC6hE6v

beam1

beam2 E6vC6hA6v

No Absorber vs. Absorber (tunnel)

Mean values ± 2m horizontally and ± 1m vertically.


42

Three Absorber Case for UJ76

Dose (Gy/y)

Dose (Gy/y)

Doses in racks ≤ 5 Gy

Similar to NoAbsorber case !

Related works:Ozone productionin IR7. Accident case studies,...

A. Pressland

Introduction

● Radiation induced production of O3 around IP7.– dose estimates provided by Fluka – assumed 4.1 1016 lost protons per year. – assumed all Fluka energy loss in air is ionizing.

● Enclosures around regions of high dose (O3 concentration)– enclosures seal the tunnel in areas where the ozone– voided independently of the main tunnel– air corridor to allow passage of tunnel air towards TU76

Tunnel Section

Energy scorings● Annual dose (GeV/cm3) based 4800 beam-hours ● Complient with the standard 104 – 105 Gy/year

Calculation (1)• Fasso et el (1982) LEP Note 379 gives the following differential equation

I = ionizing energy deposited in air per unit time, in eVcm-3s-1

G = number of ozone molecules formed, in eV-1 (7.4 10-2 eV-1) = dissociation constant for ozone, in s-1

(2.3 10-4 s-1)N = concentration of ozone at time t, in cm-3

k = decomposition constant, in eV-1cm3

(1.4 10-16 eV-1cm3)Q = ventilation rate, in cm3s-1

V = irradiated volume, in cm3

• Integration leads to the following concentration kinetics:

dNdt

IG Î±N kIN QVN

N t IGÎ± kI Q V

1 exp Î± kI Q V t

formation

dissociation

decomposition

ventilation

Calculation (2)

• More useful steady state formulation in a tunnel– average energy , Iave, is deposited per unit time– air circulates with speed v ms-1

– length z of tunnel is irradiated

This is a special case of the previous equation wherethe concentration N cm-3 increases with distance z traversedand air traverses a length z meters of tunnel in z/v seconds accumulating a concentration N(z) molecules of ozone

N zIaveG

Î± kIave1 exp Î± kIave z v

Results

● Steady state results for air exiting regions

● Assumed ventilation rates– 10 m3s-1 for the main tunnel– 0.2 m3s-1 for the enclosures

● Parts per million conversion requires– air density of 1.202 kg m-3

– molecular weight of 28.95 g mol-1 – Avogadro constant NA = 6.022 1023

NO3 (ppm) 4.3 10-38.9 10-34.63 10-4

Encl. 2Encl. 1Tunnel

Results

● Concentration kinetics using averaged dose– assumes ‘magic ventilation’ where air is not considered to travel to the

ventilation point through a radiation environment.– only useful to compare growth rates etc

Tunnel Enclosure 1 Enclosure 2

2.3 10-4 ppm5.1 10-2 ppm 2.5 10-2 ppm

25 mins300 mins

300 mins

energy deposition studies at ir7

Documents

proton energy

stored beam

skewpencil beam

tevc beam

analytic fieldtranslation

latticefrom mc2005

ratiofrom mc2005

irregular beam loss