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Computing for Science

The Computing for Science (CS) group supports ILL scientists, students and visitors in a number of activities including data analysis, instrument simulation and sample simulation.

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ILL Reactor models

The ILL Reactor Simulations Data Base

Computed by E. Farhi (ILL/DS/CS), P.A. Harraud (ILL/DS/CS) and S. Fuard (ILL/DPT/BPC) in Nov 2006. Updated in 2011.


This site gathers a comprehensive study of all beam tubes exiting the ILL heavy water reactor vessel (except the inclined tubes). Each simulation comes with its description file for MCNP and/or Tripoli, as well as spectrum, XY and angular distributions to be used for further shielding computations and propagation to the instruments, often through the guides. Interface from MNCP PTRAC and Tripoli BATCH files are available in McStas.
When available, capture fluxes are also given.


Beam tubes (hot, thermal, cold) simulated at 5.2 m

Methodology:

  1. MCNP and Tripoli models give absolute capture fluxes in [n/s/cm2]. They produce neutrons in the reactor.
  2. These neutrons are then propagated to measurement points and instrument using McStas.

The Vanne de Securite (VS) is situated at L=5.2 m distance from the core center ('Bouchon'). The capture flux measurements on beam tubes are performed there, at about 6 m from the doigt-de-gant nose.
 
Flux units are [10^10 n/s/cm2] integrated gold foil capture flux (Phi_c, from 0 to 500 meV, weighted by velocity for absorption correction).
The unweighted integrated flux is also given (Phi) from 0 to 10 Angs.

Clik on the links to access detailed information.

ILL Brilliance

From the flux estimates obtained with both MCNP and Tripoli events propagated with McStas, we extract the brilliance of a number of tubes, using the divergence measured with the McStas histograms (usually about +/-1 deg at 5.2 m). The Brilliance of cold sources is 2 1013 at maximum, and thermal tubes reach about 5-8 1013 [n/s/cm2/st/Angs] but this depends a lot on the beam tube (H10 and H11 are more intense by e.g. a factor 2). [fig in EPS][PNG]. This Data has been updated by Farhi and Calzavara on Feb 21st, 2011 [ pdf ].

Overview of measured and computed flux at beam tube


Beam tube

Measurement Capture Flux
[1010 n/s/cm2 gold foil]
(dist from core center - L=5.2 when not indicated, date)

Comment

MCNP Capture Flux 
[1010 n/s/cm2]

Tripoli Capture Flux
[1010 n/s/cm2]

H1x cold (D17, IN5, IN6, D7, IN10, D11, IN14, IN11, LADI)


2.60 (H113-1: 11.4 m, 11/08/1999)


11.0+/- 0.1 [Phi=6.8]
2.72 +/- 0.08 [at 11.4 m, Phi=1.04]

11.6 +/- 0.7 [Phi=6.9]
1.87 +/- 0.4 [at 11.4 m, Phi=.69]

H2x thermal (Vivaldi, SALSA, D1B, S18, D23, IN22, IN3, D10, IN13)


0.722 (H22-1: 11.4 m, 08/09/2003)


m=2

6.1 +/- 0.1 [Phi=7.1]
1.03 +/- 0.04 [at 11.4 m]

5.8 +/- 0.3 [Phi=7.1]
1.0 +/- 0.2 [at 11.4 m]

H3

2.51 (5.23 m, 18/06/1984)



3.4 (no hot source)

H4

2.4 (5.23 m, 18/06/1984)



1.7 (no hot source)

H5x cold (IN14, IN16, D16, D22, IN15, SuperADAM, ...)


2.0 (Dec 2006)


10.0 +/- 0.1 [Phi=7.8]
1.88 +/- 0.05 [Phi=0.74]

10.1 +/- 0.6 [Phi=7.6]
2.18 +/- 0.04 [Phi=.66]

H6-H7

4.8e14 (interieur canal, 01/02/1991)



1.1

H8

1.92 (5.23 m, 29/05/1990)



3.1 (no hot source)

H9 thermal

(PN1, Tomography)

4.7 (5.23 m,16/03/2000)

phi=200
Lohengrin collimates the beam

6.01 +/- 0.06 [Phi=7.2]

5.9 +/- 0.3 [Phi=7.1]

H10 thermal (IN8)

8.7 (5.23 m, 08/06/2001)

phi=200

8.65 +/- 0.05 [Phi=10.6]

8.2 +/- 0.4 [Phi=9.8]

H11 (D20,D19, D2B)

7.97 (5.23 m, 17/10/2000)

phi=200

7.8 +/- 0.07 [Phi=9.4]

7.2 +/- 0.04 [Phi=8.9]

H12 (IN4)

2.5 (5.23 m, 08/08/2001)

phi=100

2.56 +/- 0.07 [Phi=3.0]

2.75 +/- 0.25 [Phi=3.2]

H12n (new)


phi=200

5.96 +/- 0.07 [Phi=7.1]


H13 (IN20)

5.88 (5.23 m, all cycles)

phi=170

5.66 +/- 0.06 [Phi=6.8]

5.6 +/- 0.4 [Phi=6.6]

Table 1: Flux measured and simulated with MCNP and Tripoli at 5.2 m from the core (bouchon). Data in italic is to be taken with caution (old or geometry was changed since then).


CONCLUSION: Both MCNP and Tripoli neutrons propagated using McStas agree (nearly) perfectly with measurements.

Geometry description and other relevant information

  • Top view from RHF reactor vessel [png]
  • Side view from reactor vessel [pdf][png]
  • Gold foil measurements in ILL5 (Level C, at radius=5.2 m from core) [pdf, Feb 2005]
  • Link to the DPT/SMAE guide data base [intranet only HTML]
  • Map of the ILL [pdf, from the 2008 annual report]
  • McStas model used to transport neutrons from the reactor to the measurement point at 5.2 m [instr]
  • P. Ageron, Nucl. Instr. Meth., A284 (1989) 197.
  • E. Farhi, Internal ILL Report DS/CS­EF/08 June 24th 2004 [ pdf ].
  • E. Farhi and Y. Calzavara, ILL Report Feb 21st, 2011 [ pdf ]