[mcstas-users] mcstas-users Digest, Vol 25, Issue 3

Mon Feb 24 16:33:04 CET 2014

Dear Dr. Messaoud,

I am not quite sure I understand your request, but I shall try to
answer. Apologies if I have misunderstood you.

To simulate a single polarising supermirror, you would use the
Pol_mirror component. Take a look at Test_Pol_Mirror for an example of
how to use it.

If what you need is a spectrum for an actual physical device I'd suggest
checking the websites of the commercial vendors such as Mirrotron, Swiss
Neutronics, Misubishi, too name a few.

cheers
Erik

On 02/23/2014 03:12 PM, Morad Messaoud wrote:
> Hi, I need just example about the specter of reflectivity of a
> polariser supermirror (by reflexion and by transmission) and
> monochromator
> 
> 2014-02-06 7:36 UTC, mcstas-users-request at mcstas.org
> <mcstas-users-request at mcstas.org>:
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>>    1. Re: Fwd: Neutron Beam tracking - MCSTAS (Britt Rosendahl Hansen)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Wed, 5 Feb 2014 09:28:12 +0000
>> From: Britt Rosendahl Hansen <broh at fysik.dtu.dk>
>> To: Mar?a Freir?a L?pez <m.freiria87 at gmail.com>
>> Cc: "mcstas-users at mcstas.org" <mcstas-users at mcstas.org>
>> Subject: Re: [mcstas-users] Fwd: Neutron Beam tracking - MCSTAS
>> Message-ID: <764BA851-9CFB-4FD1-A19A-0FF60BC9170A at fysik.dtu.dk>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Hi Maria
>>
>> I think you could use the premonitor_nd and monitor_nd components to get the
>> answer you need. I suggest looking at these components in the component
>> manual.
>>
>> Feel free to write me again if you cannot get it to work.
>>
>> Regards,
>> Britt
>>
>>
>> Sent from my iPhone
>>
>>> On 05 Feb 2014, at 09:50, "Mar?a Freir?a L?pez" <m.freiria87 at gmail.com>
>>> wrote:
>>>
>>>
>>> Hello everybody,
>>>
>>> my name is Mar?a Freir?a, Master Student in Nuclear Engineering at the
>>> Technische Universit?t M?nchen. Right now I am working at my Master Thesis
>>> at the research reactor FRM II, studying the viability of a future fuel
>>> conversion.
>>>
>>> The fact is that we did some experiments at the reactor in order to
>>> measure the cold neutron spectrum for different reactor power levels.
>>>
>>> Here is a brief description of the reactor:
>>>
>>> <Beam_tubes.jpg>
>>> Several beam tubes supply various experimental stations with neutrons from
>>> different parts of the reactor. In our experiment we considered the tube
>>> SR-1 (connected to the cold source), which is subdivided into 6 smaller
>>> tubes as shown in the figure above.
>>>
>>> One of these 6 tubes (NL-4) is again divided into 2 tubes (named NL-4a and
>>> NL-4b) which lead to the 2 stations (SANS-1 and PGAA) where the measures
>>> were taken:
>>>
>>> <Experiment_Scheme_1.jpg>
>>>
>>>
>>>
>>> The obtained results concerning neutron spectrum at the 2 stations differ
>>> from each other. Eventhough the neutrons in both tubes come from the cold
>>> source, based on the results, we think that the neutrons have a different
>>> nature, due to the heterogeneous properties along the cold source. A point
>>> to be taken into account is the fill level  of the cold source (D2 -
>>> liquid deuterium aprox. 25K). Some experts suggest that the major part of
>>> the neutron flux analyzed at SANS-1 comes from the lower part of the cold
>>> source and in the case of PGAA the neutrons have their origin in the upper
>>> part of the tank (near the fill level). This would explain the different
>>> results at the 2 stations:
>>>
>>> <Experiment_Scheme_2.jpg>
>>>
>>> In order to proof this theory, we started to work with MCSTAS.
>>>
>>> I got the instruments and components defined in MCSTAS which describe the
>>> geometry of the tube structure. But, as a beginner, I need to ask for some
>>> help:
>>>
>>> I need to know the origin of the neutrons which enter the tubes NL-4a and
>>> b. In other words: from which part of the cold source do most of the
>>> neutrons come in each case (NL-4a and NL-4b):
>>>
>>> <Experiment_Scheme_3.jpg>
>>>
>>> Is it true that the neutron spectrum is different at the 2 experimental
>>> stations because the beam has its origin in different parts (the lower and
>>> the upper part) of the cold source? Or is the distribution almost
>>> homogeneous so that the beam properties in both tubes should be the same?
>>>
>>>
>>> In order to answer these questions, the suggestion made is to implement a
>>> kind of "marker" at the beginning of SR-1 divided in "n" cells. This would
>>> make it possible to know which of these neutrons "make their way" to
>>> SANS-1 and which others to PGAA.
>>>
>>> Is it viable to create such a "marker"? Or do you have any other
>>> suggestions for solving this problem?
>>>
>>> As I said, as a beginner I am not conscious of the possibilities that
>>> MCSTAS offers, that is why I was directed to you by Peter Link, Neutron
>>> Optics department at the FRM II.
>>>
>>> I hope I could explain my problem in a more or less understandable way :)
>>>
>>> I would be really greatfull for your help!
>>>
>>> Kind regards,
>>>
>>> Mar?a
>>>
>>> _______________________________________________
>>> mcstas-users mailing list
>>> mcstas-users at mcstas.org
>>> http://mailman.mcstas.org/cgi-bin/mailman/listinfo/mcstas-users
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-- 
Erik Bergbäck Knudsen, Research Engineer         | DTU | morituri
NEXMAP, DTU Fysik, DK-2800 Kgs. Lyngby, Denmark  |<>-<>|    te
phone: (+45) 2132 3151, mobile: (+45) 3123 6184  |<>-<>| salutant