[mcstas-users] TOFRes_sample

Wed Oct 25 15:28:00 CEST 2023

Dear Ryoichi,

I believe your understanding of the component geometry is correct, and in fact there was a minor logical issue for the case of thickness=0.
(In the attached t1 and t2 are derived from the “outer hollow” both in the case of thickness=0 or if hollow exists but is not hit - including use of || instead of &&)

I have further taken the time to clean up a few lines of “dead code” and have dusted of a VERY old test instrument that I found, ported for use with 3.4.

Finally I have attached a new TOFRes_monitor.comp - which for structural reasons is now needed.
(We use a macro that makes use of the literal Res_sample / TOFRes_sample label to figure out what parameter struct needs to be probed.)

In other words, Res_sample and Res_monitor is a pair, TOFRes_sample and TOFRes_monitor is a slightly different pair…. Slightly annoying.

I may eventually merge the two sample components allowing two different “modes” to get rid of this new derived monitor, but that will have to wait.

I have run a quick test with the attached files and McStas 3.4 - and produce normal “Res_monitor” like output, so I think this should be an OK solution for now.

Please try it out for yourself and come back with your findings.

All of the attached codes are also uploaded to the main branch on GitHub and any comments/further revisions are most welcome, e.g. on
https://github.com/McStasMcXtrace/McCode/issues/1512

Best,
Peter

On 25 Oct 2023, at 08.04, Ryoichi Kajimoto <ryoichi.kajimoto at j-parc.jp> wrote:

Dear Kim,

To my understanding, the meaning of the code is like the attached figure. Is my understanding correct?
If this is correct, l_full becomes large when thickness is large, while scat_factor = 2*(radius-thickness) becomes small. Then l_full/scat_factor becomes extremely large.

With regard to this, I found that when thickness = 0, which is default, or thickness = radius, the code does not generate an output data. (I tested this with McStas 2.7.2)

I guess that:
- When thickness = 0, t1 = t0 and t3 = t2. This results in l_full = p = 0.
(Function cylinder_intersect(&t1, &t2, x, y, z, vx, vy, vz, radius-thickness, yheight) in line 167 is executed even when thickness = 0.)
- When thickness = radius, scat_factor becomes zero, and p becomes infinity (divided by zero).

Best regards,

Ryoichi

Kim Lefmann wrote on 2023/10/24 18:58:
Dear Ryoichi,
You are right that in this case scat_factor becomes small - but so does l_full since materials thickness is small. So the fraction is in any case of the order 1.
Of course if you were interested in absolute intensities, the cross section should be weighted differently, as we do in the more realistic samples.
best, Kim
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
*From:* Ryoichi Kajimoto <ryoichi.kajimoto at j-parc.jp>
*Sent:* Tuesday, October 24, 2023 11:14:59 AM
*To:* Kim Lefmann; pkwi at dtu.dk
*Cc:* mcstas-users at mcstas.org
*Subject:* Re: [mcstas-users] TOFRes_sample
[You don't often get email from ryoichi.kajimoto at j-parc.jp. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification <https://aka.ms/LearnAboutSenderIdentification> ]
Dear Kim,
Thank you for explaining the detail.
Maybe I understand.
My question is that if scat_factor = 2*(radius-thickness), it becomes very small when thickness is nearly equal to radius. Then l_full/scat_factor becomes extremely large, which seems to be unreasonable.
Anyhow it may not be a problem because the absolute intensity is not important in resolution calculation.
Best regards,
Ryoichi
Kim Lefmann wrote on 2023/10/24 17:34:
Dear Ryoichi,

Since I wrote the code, please let me explain the logic.

For a resolution calculation, the absolute intensity is irrelevant, since you only want to know the widths.

The weighing using the fraction l_full/scat_factor is done to correct for the fact that the outer parts of the sample scatter differently from the center part due to different path lengths:

l_full is exactly the path length in the sample of this neutron ray
scat_factor is the path length for a ray that hits the sample center (and is constant for the full simulation).

The latter path length is used as normalization (and to ensure that the units are correct).

best, Kim

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
*From:* mcstas-users <mcstas-users-bounces at mcstas.org> on behalf of Ryoichi Kajimoto <ryoichi.kajimoto at j-parc.jp>
*Sent:* Tuesday, October 24, 2023 9:40:56 AM
*To:* pkwi at dtu.dk
*Cc:* mcstas-users at mcstas.org
*Subject:* Re: [mcstas-users] TOFRes_sample

[You don't often get email from ryoichi.kajimoto at j-parc.jp. Learn why this is important at  https://aka.ms/LearnAboutSenderIdentification <https://aka.ms/LearnAboutSenderIdentification> <https://aka.ms/LearnAboutSenderIdentification <https://aka.ms/LearnAboutSenderIdentification>> ]

Dear Peter,

Wrt. the scat_factor, since thickness is an optional parameter (default=0, parametrises an optional "inner hollow”) I believe the formula is OK.
Thanks, but there is a line in line 176:
       p *= l_full/scat_factor;      /* Scattering probability */
where l_full is "Length of full path through sample."

It seems to me that p is defined as the ratio of length of full path through sample to total size of sample. However, if scat_factor is as it is, p can be larger than unity.

Best regards,

Ryoichi

Peter Kjær Willendrup wrote on 2023/10/24 16:12:
Dear Ryochi,

Once I have the edits in place and a running instrument I will send the modified component to this mailinglist thread.

Wrt. the scat_factor, since thickness is an optional parameter (default=0, parametrises an optional "inner hollow”) I believe the formula is OK.

Best
Peter

On 24 Oct 2023, at 07.20, Ryoichi Kajimoto <ryoichi.kajimoto at j-parc.jp> wrote:

Dear Peter,

Thank you for the prompt response. I hope this issue will be solved soon.

I have another question regarding TOFRes_sample.

On line 169 of TOFRes_sample.comp, there is a code:
       scat_factor = 2*(radius-thickness);

But is this correct? I think scat_factor should be 2*radius.

Best regards,

Ryoichi

Peter Kjær Willendrup wrote on 2023/10/24 3:07:
Dear Ryoichi Kajimoto,

Thank you for reporting this issue, you are completely right in pointing out that needed modifications are missing in the McStas 3.4 version of TOFRes_sample.
(This has gone unnoticed since a test-instrument for the said component was not defined in our test suite, sorry for this.)

I have defined a GitHub issue at https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMcStasMcXtrace%2FMcCode%2Fissues%2F1512&data=05%7C01%7Clefmann%40nbi.ku.dk%7Cde77aece11cf4918c23008dbd471b476%7Ca3927f91cda14696af898c9f1ceffa91%7C0%7C0%7C638337357056579252%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=94nRHavpkrZdgXTsClxXqFXDpVH5DuAZ1gf9tER8tpM%3D&reserved=0 <https://github.com/McStasMcXtrace/McCode/issues/1512> <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMcStasMcXtrace%2FMcCode%2Fissues%2F1512&data=05%7C01%7Clefmann%40nbi.ku.dk%7Cde77aece11cf4918c23008dbd471b476%7Ca3927f91cda14696af898c9f1ceffa91%7C0%7C0%7C638337357056579252%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=94nRHavpkrZdgXTsClxXqFXDpVH5DuAZ1gf9tER8tpM%3D&reserved=0 <https://github.com/McStasMcXtrace/McCode/issues/1512>> and will implement the needed
changes as soon as time allows.

Best,
Peter Willendrup

On 23 Oct 2023, at 13.29, Ryoichi Kajimoto <ryoichi.kajimoto at j-parc.jp> wrote:

Hi,

I'm simulating a resolution function of a direct-geometry TOF spectrometer. I use TOFRes_sample() for the sample and Res_monitor() for the monitor.

My code worked with McStas 3.1, but it cannot be compiled with McStas 3.4.
I would appreciate if you could provide any solution.

Converting the .instr file to .c with mcstas command worked fine without an error, but compiling it with gcc -O3 -lm stops with an error message attached below.

I found that Res_monitor.comp and Res_sample.comp were greatly updated in McStas 3.4 but TOFRes_sample.comp was unchanged. I suspect that TOFRes_sample.comp is not compatible with Res_monitor.comp...

Thank you in advance,

Ryoichi Kajimoto

==================================

SIKIResSim.c: In function ‘Table_Read_Handle’:
SIKIResSim.c:7518:60: warning: format ‘%i’ expects argument of type ‘int’, but argument 5 has type ‘long int’ [-Wformat=]
7518 |       fprintf(stderr,"Warning: Read_Table :%s %s Data has %i invalid lines (*****). Ignored.\n",
      |                                                           ~^
      |                                                            |
      |                                                            int
      |                                                           %li
......
7521 |         count_invalid);
      |         ~~~~~~~~~~~~~
      |         |
      |         long int
SIKIResSim.c: In function ‘_resmonitor_setpos’:
SIKIResSim.c:13221:6: error: ‘RSsample’ undeclared (first use in this function)
13221 |   if(RSsample && strlen(RSsample))
      |      ^~~~~~~~
SIKIResSim.c:13221:6: note: each undeclared identifier is reported only once for each function it appears in
SIKIResSim.c: In function ‘class_Res_monitor_init’:
SIKIResSim.c:663:33: warning: format not a string literal and no format arguments [-Wformat-security]
663 | #define NAME_CURRENT_COMP (_comp->_name)
      |                           ~~~~~~^~~~~~~~
SIKIResSim.c:13781:48: note: in expansion of macro ‘NAME_CURRENT_COMP’
13781 |   if (!strcmp(filename,"\0")) sprintf(filename,NAME_CURRENT_COMP);
      |                                                ^~~~~~~~~~~~~~~~~
SIKIResSim.c:641:10: error: ‘_class_Res_sample_parameters’ undeclared (first use in this function); did you mean ‘_class_TOFRes_sample_parameters’?
641 |     &( ((_class_ ## type ##_parameters *) _getvar_parameters(compname))->par )
      |          ^~~~~~~
SIKIResSim.c:13835:18: note: in expansion of macro ‘COMP_GETPAR3’
13835 |   int *index_ptr=COMP_GETPAR3(Res_sample, res_sample_comp, compindex);
      |                  ^~~~~~~~~~~~
SIKIResSim.c:641:41: error: expected expression before ‘)’ token
641 |     &( ((_class_ ## type ##_parameters *) _getvar_parameters(compname))->par )
      |                                         ^
SIKIResSim.c:13835:18: note: in expansion of macro ‘COMP_GETPAR3’
13835 |   int *index_ptr=COMP_GETPAR3(Res_sample, res_sample_comp, compindex);
      |                  ^~~~~~~~~~~~

==================================

This is how I use TOFRes_sample() and Res_monitor():

==================================

SPLIT COMPONENT RSsample = TOFRes_sample(
thickness = sample_r-0.0001,
radius = sample_r,
yheight = sample_h,
focus_xw = Wdx+0.001,
focus_yh = Wdy+0.001,
target_x = sample_det_x,
target_y = sample_det_y,
target_z = sample_det_z,
time_bin = (ts+tsd+toffset)*1e6,
time_width = Dtsd*1e6
) AT (0,0,L1) RELATIVE mod

COMPONENT det_pos = Arm()
AT (sample_det_x,sample_det_y,sample_det_z) RELATIVE RSsample
ROTATED (0,atan(sample_det_x/sample_det_z)*RAD2DEG,0) RELATIVE RSsample

COMPONENT resmonitor = Res_monitor(
res_sample_comp = RSsample,
options = "cylinder",
xwidth = Wdx, yheight = Wdy,
filename = "resmonitor.dat"
) AT (0,0,0) RELATIVE det_pos
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Peter Kjær Willendrup
Forskningsingeniør, Specialkonsulent

DTU Physics
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Technical University of Denmark

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Main office at
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pkwi at fysik.dtu.dk<mailto:pkwi at fysik.dtu.dk <mailto:pkwi at fysik.dtu.dk <mailto:pkwi at fysik.dtu.dk>>>

Peter Kjær Willendrup
Forskningsingeniør, Specialkonsulent

DTU Physics
[image001.gif]

Technical University of Denmark

[image002.gif]

Department of Physics
Fysikvej
Building 307
DK-2800 Kongens Lyngby

Main office at
ESS DMSC
COBIS, Ole Maaløes vej 3, 2200 København N, Denmark

Direct +45 2125 4612
Mobil +45 2125 4612
Fax +45 4593 2399
pkwi at fysik.dtu.dk

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