Vanadium Sample

[Kristian Nielsen]

> Date: Wed, 23 Jun 1999 09:04:20 +0200 (MET DST)
> From: Stephan Roth <Stephan_Roth at Physik.TU-Muenchen.DE>

> Dear Sir,
> 
> I am using McStas for the construction of a disc chopper time-of-flight
> spectrometer of IN5-type. Especially I want to simulate angular resolved

> But a detector placed at the focusing point counts no neutrons.
> Hence I would like to ask you, if you could help me finding the mistake in
> the setup (I have incorporated the in5.instr file in this mail). 

(I just returned from holiday, which is why I did not reply until
now. So maybe you already solved your problem, but here is an answer
just in case).

Ok, I found two problems in your definition:

1. The first monitor overlaps with the sample. McStas does not deal very
   well with this situation.
2. The final monitor is parallel to the beam! It needs to be rotated to
   be perpendicular to the scattered beam from the sample.

After fixing these two problems, the simulation produces neutrons in the
final detector.

I have attached the modified instrument definition. I also put the file
on our web page, at

    http://neutron.risoe.dk/mcstas/support/roth/in5.instr

 - Kristian.

--
Kristian Nielsen        kristian.nielsen at risoe.dk
Risø National Laboratory
Condensed Matter Physics and Chemistry Department
Tel. +45 4677 5515   Fax +45 4677 4790

-------------- next part --------------
DEFINE INSTRUMENT detektest()

TRACE 
COMPONENT arm = Arm() AT (0,0,0) ABSOLUTE

COMPONENT source = Source_div(width=.02,height=.05,hdiv=.702,vdiv=.702,E0=2.2722,dE=.001)
	AT (0,0,0) RELATIVE arm

COMPONENT guide = Guide(w1=.02,h1=0.05,w2=.02,h2=0.05,l=53,R0=0.995,
			Qc=.0214,alpha=5.566,m=1,W=.0033)
	AT (0,0,0.001) RELATIVE source

COMPONENT detector1=Monitor(xmin=-.1,xmax=.1,ymin=-.2,ymax=.2)
	AT (0,0,0.190) RELATIVE guide

COMPONENT sample1=V_sample(radius_i=.0143,radius_o=.0148,h=.05,pack=1,focus_r=.1,
				target_x=4,target_y=0,target_z=0)
 AT (0,0,.205) RELATIVE guide

/*
COMPONENT slit_det=Circular_slit(radius=.1)
 AT (4.000,0,0) RELATIVE sample1
*/

COMPONENT detector1f=Monitor(xmin=-.2,xmax=.2,ymin=-.2,ymax=.2)
 AT (4,0,0) RELATIVE sample1
 ROTATED (0,90,0) RELATIVE sample1

END