Study on Thermal Deposition in the Interaction Region Magnets

CARE 06INFN–LNF 15-17 November 2006

Study on Thermal Deposition in the Interaction Region

Magnets

[email protected]

[email protected]

mailto:[email protected]




Outline

• Chronology (where this study comes from)

• Method of calculations

• Cases and results

• 2005/06 reprise of the problem

• Work done this year

• Next


Chronology

• Study of a new Nb3Sn design for the LHC insertion quad started in 1995, suggested by the Milan group (L.Rossi)

• Ended in 1998 (1999 final report)


Purpose of the Study was:

• Use of the Nb3Sn technology instead of the "traditional" NbTi, for the construction of the focussing quadrupoles in the interaction region of LHC in order to have :

Higher focussing gradient (higher luminosity), in the same magnet aperture

or The same focussing gradient in a larger aperture,

(easier beam dynamics, especially at the injection).


Thermal Analysis

(2D ANSYS) DTUJET

Tracking of the

secondary

particles (ad hoc code)

Evaluation of the

power distribution

in the various

elements

(FLUKA)

1300 p-p 7 TeV events

Calculation Procedure

The thermal analysis is a very important issue in this problem, because a good cooling system in the magnet allow to operate the magnets in very high radiation environment with a good safety margin.

This coupling with the thermal analysis was the key and innovative part of this study


“Old” Cases Studied

Case Number

Aperture (mm)

Main Gradient

(T/m)

Trim Gradient

(T/m)

Absorbers Type / Thickness (mm)

1 70 235 82 No 2 70 235 82 Cylindrical uniform / 5 3 70 300 105 No 4 85 235 82 No 5 70 227 80 Suited / 12; 10; 4.5; 4.5; 4.5

Version LHC 6.5 with G = 203 T/m and Beam Screens


Modelization and Hypothesis

TRACKING• Beam pipe thickness 1.5 mm• Detector peak field 2 T• Detector radius 1.1 m• Detector length 5.3 m• Crossing angle 200 rad • Cross section

(inel.+ single diff. event) 80 mbarn• Luminosity 1034 cm-2s-1

THERMAL ANALYSISMODEL 2D - Steady StateThermal Conductivity Computed from cable-insulation stackInsulation Non isotropic G10Heat flux Purely longitudinalHeat transfer coefficient 1000 W/m2K at 1.9 K

FLUKA• Cut off for Hadrons 1 MeV• Cut off for electrons/positron 1.5 MeV• Cut off for photons 0.2 MeV• Cut off for neutrons 0.4 eV

Detailed description of the magnets with the coil layers, insulation, wedges and yokes


Total Power into the Quads and the Inner Conductor Layer

Total Power in the Quads and in the Adsorbers (W)

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11

Q1

Absorber (Q1)

Q2a

Absorber (Q2a)

Q2b

Absorber (Q2b)

Q3

Absorber (Q3)

Q01

Absorber (Q01)

=70 mm G=235 T/m

GQ01=82 T/m

=70 mm G=235 T/m

GQ01=82 T/mUniform

Absorbers

=70 mm G=300 T/m

GQ01=105 T/m =85 mm G=235 T/m

GQ01=82 T/m

=70 mm G=227 T/m

GQ01=80 T/m Suited

Adsorbers

Power in the First Shell of Q2a (W)

0

0.5

1

1.5

2

2.5

3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

=70 mm G=235 T/m

GQ01=88 T/m

=70 mm G=235 T/m

GQ01=88 T/m Uniform

Adsorbers

=70 mm G=300 T/m GQ01=105

T/m=85 mm

G=250 T/m GQ01=88

T/m

=70 mm G=227 T/m

GQ01=80 T/m

With Suited Adsorbers

Note the negative effect of the uniform cylindrical adsorbers (startup of the cascade from particles that would freely travel, deposing their energy in the following, less critical quads).


Summary of the “old” casesCase Total power (W) Peak Power in Q2a (mW/cm3) Thermal Behaviour

Q1 Q01 Q2a Q2b Q3 Volume (cm3) Collar max. Temp. (K)

Peak flux

12.2 [12.5]

2.9 [3.13]

0.6 mat. Coil Layer1 peak B W/m2

1 (70-235-82) 11.5 8.7 22.4 7.5 17.4 3.2 5.1 7.2 s.steel

Al 2.6

2.33 2.45 2.33

2.24 2.11

46 31

2 (70-235-82 unif. abs.)

12.1 (5.6)

6.5 (5.0)

27.5 (11.0)

10.3 (8.5)

14.5 (11.0)

5.7 8.2 9.8 -- -- -- -- --

3 (70-300-105) 14.4 11.0 25.3 9.5 20.4 4.1 7.5 -- s.steel

Al 2.74 2.45

2.6 2.45

2.3 2.15

56 41

4 (85-235-82)

10.6 8.2 19.4 8.0 6.3 3.8 5.0 -- s.steel Al

2.43 2.25

2.34 2.25

2.12 2.05

33 26

5 (70-227-80 suited abs.)

13.3 (12.2)

4.5 (4.3)

10.8 (4.9)

7.8 (5.3)

14.6 (10.6)

-- 0.3 0.7 -- -- -- -- --

The statistical error has been evaluated from different runs with independent random seeds

• 1% for the region binning

• 3% medium binning (Bin Volume = 0.5x0.5x50 = 12.5 cm3)

• 4% small binning ( " " = 0.25x0.25x50 = 3.1 cm3)

• 7% very small binning ( " " = 0.25x0.25x10 = 0.63 cm3)


Indications from the”old” cases I• Negative effect of the cylindrical absorbers

• The case with higher gradient (G=300 T/m) is slightly worst than the reference case (G=235 T/m)

• Case with lager aperture (=85 mm) is better for the deposed power but it has a small increment in the peak power.

• From the thermal analysis the power released by the radiation does not endanger the operating point of the magnets and guarantee a good stability margin, as a matter of fact the maximum temperature is in the median plane, where the magnetic field is lower enough to guarantee a safe combination of the two parameters.

• Conversely in the higher field regions the temperature increment is not too high .

• Larger stability margin can be achieved by using the aluminum collars instead of the stainless steel ones (tradeoff with the mechanical properties).

• Nb3Sn is a good solution for the second generation low- quads, either to increase the focussing gradient, or to get the same focussing performance in a larger aperture.


Indications from the”old” cases II

In the “nominal (academic) case” or LHC version 6.5 with beam screens:

• quad aperture; 70 mm ;

• quad gradient; 235/203 T/m;

• trim quad between Q1 and Q2a; 82 T/m

The most loaded quad is the second or the last one (Q2a,Q3), absorbing some 25-35 W with a peak power of about 7-10 mW/cm3

(depending on the bin volume)

With the actual luminosity value L=1034 cm2s-1

Indication of a positive effect by opening the aperture, this lead to consider large (100 mm) quad aperture for the “new” studies


New Studies

Approaching the triplet to the IP opens the possibility of an increased focusing and hence of a significantly larger luminosity (J.-P. Koutchouk)

Conversely the energy deposition in the magnets becomes a critical point, because of the different secondary beam dynamics and the increased power

Why moving towards IP ?

What the energy/power deposed in the magnets if moving closer to IP


HypothesisTRACKING

• Beam pipe aperture 58.0 - 34.0 mm (TAS) - 95.5 mm (Beam screens after the TAS are taken into account)

• Detector Solenoid Field with its fringing field (theoretical)• Detector peak field 2 T (ATLAS)• “ radius 1.1 m• “ length 5.3 m• Hard edge approx. for the quadrupole field

FLUKA• Quad aperture 100.0 mm• Accurate definition of the quadrupole structure

(current, insulation, wedges, collars, yokes)

• Magnetic field in the quad material (ROXIE)

• Cut off for Hadrons 1 MeV• Cut off for electrons/positron 1.5 MeV• Cut off for photons 0.2 MeV• Cut off for neutrons 0.4 eV

Cross section = 80 mbarn(inel.+ single diff. event)


Geometry and materials

G10 Insulation (0.2, 0.7, 0.5 mm)

Nb3Sn Current shells (15 mm, 60°)

S.S. Pole wedges

S.S. Collar (20 mm)

Fe Yoke (18 cm)

S.S. Beam pipe (1.75 mm)

S.S. Beam screen with cooling tubes


Cases studiedDistance IP – Q1 = 23 m ; L = 8.64 1034 cm2s-1

Quad Gradient = 193 T/m ;cr = 512 rad

0 10 20 30 40 50 60-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Ve

rtic

al Dump

Dump

Dump

Dump

Dump

TAS

Q3Q2bQ2aQ1

DetectorSolenoid

Hor

izo

nta

l Co

ord

ina

te (

cm)

z(m)

0 10 20 30 40 50 60-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Dump

Dump

Dump

Dump

Dump

TAS

Q3Q2bQ2aQ1

DetectorSolenoid

Ho

rizo

nta

l Co

ord

ina

te (

cm)

z(m)

Distance IP – Q1 = 19 m ; L = 8.67 1034 cm2s-1






(As from J.-P. K. computations)


Results I (mean values)

Total Power in the Quadrupoles

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

Q1

Q2a

Q2b

Q3

Ip - Q1 = 23 mL = 8.64E34

cr = 512 radG = 193 T/m

IP - Q1 = 19 mL = 8.67E34

cr = 514 radG = 204 T/m

IP - Q1 = 16 mL = 8.72E34

cr = 507 radG = 208 T/m

IP - Q1 = 13 mL = 8.77E34

cr = 500 radG = 213 T/m

Pow

er (W

)

The power is increased of about one order of magnitude, respect to the actual case, because of the corresponding increase of the Luminosity

The study is a parametric one, so it is should be used to check the effects of the insertion moving.

Cut-offs values and biasing option in order to have “reasonable” CPU Time (~ 60 hours on Intel Centrino 2 GHz for each configuration)

More accurate absolute values can be obtained with different calculation option and higher CPU times.

PTAS~ 1 kW

Pcharged ~ 60%

Pneutral ~ 40%

15 % Hadron

73 % em showers


Results II(mean values)

Power in the First Shell of Q2a

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Pow

er (W

)

Ip - Q1 = 23 mL = 8.64E34

cr = 512 radG = 193 T/m

IP - Q1 = 19 mL = 8.67E34

cr = 514 radG = 204 T/m

IP - Q1 = 16 mL = 8.72E34

cr = 507 radG = 208 T/m

IP - Q1 = 13 mL = 8.77E34

cr = 500 radG = 213 T/m

Power in the First Shell of Q2b

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Pow

er (W

)

Ip - Q1 = 23 mL = 8.64E34

cr = 512 radG = 193 T/m

IP - Q1 = 19 mL = 8.67E34

cr = 514 radG = 204 T/m

IP - Q1 = 16 mL = 8.72E34

cr = 507 radG = 208 T/m

IP - Q1 = 13 mL = 8.77E34

cr = 500 radG = 213 T/m

Power in the First Shell of Q3

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

Pow

er (W

)

Ip - Q1 = 23 mL = 8.64E34

cr = 512 radG = 193 T/m

IP - Q1 = 19 mL = 8.67E34

cr = 514 radG = 204 T/m

IP - Q1 = 16 mL = 8.72E34

cr = 507 radG = 208 T/m

IP - Q1 = 13 mL = 8.77E34

cr = 500 radG = 213 T/m

Power in the First Shell of Q1

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Pow

er (W

)

Ip - Q1 = 23 mL = 8.64E34

cr = 512 radG = 193 T/m

IP - Q1 = 19 mL = 8.67E34

cr = 514 radG = 204 T/m

IP - Q1 = 16 mL = 8.72E34

cr = 507 radG = 208 T/m

IP - Q1 = 13 mL = 8.77E34

cr = 500 radG = 213 T/m


Results III(peak values)

-10-8

-6-4

-20

24

68

10 -10-8

-6-4

-20

24

68

100.00

0.01

0.02

0.03

0.04

0.05

0.06

Pmax

=0.805 W ; 64.4 mW/cm3

Density Power in a Section of Q2a

Bin volume = 0.5x0.5x50=12.5 cm3

Distance IP - Q1 = 23 m

Pow

er D

ensi

ty (

W/c

m3 )

Y (cm)

X (cm)

The maximum peak power deposition occurs in the second quadrupole (Q2a)Dist. IP –Q1(m) Pmax (W) P spec (W/cm3)

23 8.048584E-01 6.438867E-02 19 6.840063E-01 5.472050E-02 16 8.147817E-01 6.518254E-02 13 7.614822E-01 6.091858E-02

5 10 15 20 25 30 35 40 45 50-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

max=180°

Bin Volume = 0.5x0.5x50 = 12.5 cm3

Pmax

13 m from IP

16 m from IP

TAS

TAS

Q2a

Q2a

Q2b

Q2b

Q3

Q3

Q1

Q1

P (

w/c

m3 )

Distance from IP (m)

10 15 20 25 30 35 40 45 50 55-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

max=180°

Bin Volume = 0.5x0.5x50 = 12.5 cm3

Pmax

19 m from IP

23 m from IP

TAS

TAS

Q2a

Q2a

Q2b

Q2b

Q3

Q3

Q1

Q1

P (

w/c

m3 )



Results IV(peak values)

0.00

0.01

0.02

0.03

0.04

0

30

60

90

120

150

180

210

240

270

300

330

0.00

0.01

0.02

0.03

0.04

(r = 5.3 cm)

Bin Volume = 0.5x0.5x50 = 12.5 cm3

IP - Q1 = 23 m

Pow

er (

W/c

m3 )

Power Density Distribution in Q1

23.75 m from IP 24.25 m 24.75 m 25.25 m 25.75 m 26.25 m 26.75 m 27.25 m 27.75 m 28.25 m 28.75 m 29.25 m 29.75 m

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0

30

60

90

120

150

180

210

240

270

300

330

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

(r = 5.3 cm)Power Density Distribution in Q2a

Pow

er (

W/c

m3 )

IP - Q1 = 23 m

Bin Volume = 0.5x0.5x50 = 12.5 cm3

32.75 m from IP 33.25 m 33.75 m 34.25 m 34.75 m 35.25 m 35.75 m 36.25 m 36.75 m 37.25 m 37.75 m

0.000

0.005

0.010

0.015

0.020

0

30

60

90

120

150

180

210

240

270

300

330

0.000

0.005

0.010

0.015

0.020

Pow

er (

W/c

m3 )

Bin Volume = 0.5x0.5x50 = 12.5 cm3 IP - Q1 = 23 m

(r = 5.3 cm)Power Density Distribution in Q2b

39.75 m from IP 40.25 m 40.75 m 41.25 m 41.75 m 42.25 m 42.75 m 43.25 m 43.75 m 44.25 m 44.75 m

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

0

30

60

90

120

150

180

210

240

270

300

330

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

Bin Volume = 0.5x0.5x50 = 12.5 cm3

IP - Q1 = 23 m

(r = 5.3 cm)Power Density Distribution in Q3

Pow

er (

W/c

m3 )

48.25 m from IP 48.75 m 49.25 m 49.75 m 50.25 m 50.75 m 51.25 m 51.75 m 52.25 m 52.75 m 53.25 m 53.75 m 54.25 m 54.75 m


Results V(peak values)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0

30

60

90

120

150

180

210

240

270

300

330

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

(r = 5.3 cm)

Bin Volume = 0.5x0.5x50 = 12.5 cm3

Pow

er D

ensi

ty (

W/c

m3 )

(at z position where the maximum power deposition occurs)Power Density in Q2a

IP-Q1 = 23 m cr = 512 rad

IP-Q1 = 19 m cr = 514 rad

IP-Q1 = 16 m cr = 507 rad

IP-Q1 = 13 m cr = 500 rad

The asymmetric distribution is due to the crossing angle (in these cases it is higher

than the actual LHC parameter of 200 rad)


What indications ?The power deposed in the TAS is almost constant for all the cases

The total power deposed into the quads increases, approaching the IP

The power deposition in Q1 and in its first shells increase almost linearly, approaching the IP

The power deposition in Q3 increase too, but the behaviour is less “linear”

The peak power is almost constant for all the situations examined

The “hottest” quads is Q2a for IP-Q1 = 23 m while in the other cases the hottest one is Q3

The highest peak power deposition is in Q2a and it is almost constant for all the cases studied

The power distribution in the last quad is more spreaded


What’s Next ?Complete this study with a thermal analysis of the quad behaviour

Carefully evaluate the actual LHC insertion (LHC 6.5 layout) with :

• Very detailed description of the layout with NbTi coils (valves, flanges etc..)

• Take into account the tile calorimeter and the engineering of the detector

• Effect of the detector field (2 Tesla ATLAS, IP1; 4 Tesla CMS, IP5)

• Compare (if some difference is evident) between NbTi and Nb3Sn (academic/FLUKA exercise?) 0 10 20 30 40 50 60

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

Tile cal

Valves

Beam pipe tapers

Q3Q2bQ2aQ1

TAS

Detector solenoid

Ho

rizo

nta

l co

ord

ina

te (

cm)


•Get values as accurate as possible by “playing” with the cut-off and biasing parameters

•Update the event generator from DTUJET to DPMJET (not big changes expected)


New Options/Solutions

•Dipole first

•Small Dipole first

•Light quads

Every solution or possibility can/should be checked

0 2 10 4 4 10 4 6 10 4 8 10 4 0.0010.4

0.6

0.8

1Crossing Angle L. Reduction Factor

Crossing angle (urad)

Red

ucti

on F

acto

r

1

0.404564

F cr

0.0010 cr

The power in the TAS is almost constant for all the positions


Thanks

• G.Battistoni(INFN), A. Ferrari and the CERN FLUKA Group

• J.-P. Koutchouk (parameters for the study)

• C. Vollinger (ROXIE quad field map)

• C.Hoa, E. Wildner, G. Sterbini for the fruitful discussions and help in developing the study

Study on Thermal Deposition in the Interaction Region Magnets

Documents

Transcript of Study on Thermal Deposition in the Interaction Region Magnets