Re: Killing Photons

Help: Forums, postings and threads

Forums, postings and threads

Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.

Layout of the posting thread(s)

The posting threads can be shown with/without the text of the postings ("Inline depth"). In addition the depth of the thread can be controlled ("Outline depth"). For both cases several values are provided, which can be toggled. Note that the displayed values are those, which can be chosen, they do not correspond to the actual display status of the thread(s).

Add message

Add a new posting thread to this Forum

Show subscribers

Click "Show subscribers" to get the List of all subscribers, who receive e-mail from postings to this Forum, if they have not explictly unsubscribed from a posting thread. This includes:

Subscribers to the forum
Explicit subscribers to the posting or any of its ancestors
The author of the posting (if he has not unsubscribed)
The authors of any ancestor posting (if they have not unsubscribed)

Some browsers display old pages from the cache

Some browsers (e.g. Firefox) display a page from the cache even though the page has been updated. As a result, one may not get the latest messages in the forum's outline or the logon ID of the previous session appears on the upper right corner. If one suspects that he or she does not get the latest content of a page, try clearing up the personal data from the browser's cache as the following:

Tools -> Clear Private Data -> Clear Private Data (from browser Firefox)

Tools -> Delete Private Data (from browser Opera)

then reflesh the current page to get the latest content.

Details on "Inline depth" and "Outline depth"

Threads and the follow-up messages are numbered. There is one line per posting, normally starting with the posting number. The URLs of a posting and its responses reflect the depth of the follow-up postings. Watch the URLs to see how this is done. Depending on the chosen display options, the thread-display may be incomplete; the number of messages at the next level is, however, displayed, e.g. "…3 message(s)". You may not see all contributors unless you choose "All".

Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.

Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.

Argument Default value Alternative Comment

1 0 1 no text / full text of posting

2 1 All text for level 1 only / text for All postings

Argument	Default value	Alternative		Comment
1	0	1		no text / full text of posting
2	1	All		text for level 1 only / text for All postings

Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.

Argument Default value Alternative Comment

1 2 1 2 levels / 1 level (original posting)

2 3 2 3 levels / 2 levels

3 3 All 3 levels / all levels (all postings)

Argument	Default value	Alternative	Comment
1	2	1	2 levels / 1 level (original posting)
2	3	2	3 levels / 2 levels
3	3	All	3 levels / all levels (all postings)

Hi Greg,

> I've tried G4UserLimits and G4UserSpecialCuts in DetectorConstruction

> and PhysicsList, respectively, as an example I found seemed to describe.

> However, this compiles successfully and then can't run (I get errors

> telling me I need to construct electrons!), so if you suggest these

> methods please be very specific about what I need.

I can't find a reason why you'd need to define an electron simply because you are using G4UserLimits and G4UserSpecialCuts. You'll need an electron if you have this code in your PhysicsList:

  // Use Birks Correction in the Scintillation process

  G4EmSaturation* emSaturation = G4LossTableManager::Instance()->EmSaturation();

  theScintProcess->AddSaturation(emSaturation);

One way to get an electron would be to add:

G4LossTableManager::Instance();

at the top of your PhysicsList.

> I'd like to kill a photon like this (say, after a certain number of

> steps) so my program can move on and calculate the next photon

> trajectory. Any ideas on the simplest way to do this?

Well, the simplest way is G4UserLimits/G4UserSpecialCuts. Else, you can program in your SteppingAction class a private member bounceLimit which you initialize in the constructor. You also add counterBounce as a private member which you have to set to zero at each first step of a photon track. In UserSteppingAction:

case FresnelReflection:

case TotalInternalReflection:

counterBounce++;

if (bounceLimit > 0 && counterBounce >= bounceLimit) theTrack->SetTrackStatus(fStopAndKill);

(please see the examples/extended/optical/LXe/LXeSteppingAction.cc for how you obtain the G4OpBoundaryProcess status)

You can also even more simply code:

if(theTrack->GetTrackLength() > 10*m)theTrack->SetTrackStatus(fStopAndKill);

>I've also tried to set an absorption length in the fiber material, but

>when I do this the application ignores the boundary process/refractive

>indexes I've set and just shoots photons straight through my material.

I have no explanation for this!!! There is something very fishy with your code.

Best regards, Peter