Home » PANDA » PandaRoot » General » Constant magnetic field instead Solenoid Field maps
 Constant magnetic field instead Solenoid Field maps [message #14905] |
Mon, 01 July 2013 21:36  |
Anastasia Karavdina
Messages: 76
Registered: May 2010
Location: Mainz, Germany
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continuous participant |
From: *kph.uni-mainz.de
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Dear all,
As the luminosity detector group learnt during the last coll.meeting, solenoid magnetic field can't be 2T in all beam momentum range and for energies below ~3 GeV is should be 1T.
As far as I know, there is unique set of maps for solenoid field which is used for all energies. Is it possible to generate field maps for 1.5 GeV with 1T solenoid field? Whom we should ask to do it?
In meanwhile, since for LMD we have many troubles @1.5GeV, I'm trying to do tests with constant field instead loading maps for Solenoid Field. The idea is use Bz=1T for this constant field. But for cross-check with results obtained with standard solenoid maps I'm using 2T in 1st test.
The part of macro code looks like this:
PndMultiField *fField= new PndMultiField();
PndTransMap *map_t = new PndTransMap("TransMap", "R");
PndDipoleMap *map_d1 = new PndDipoleMap("DipoleMap1", "R");
PndDipoleMap *map_d2 = new PndDipoleMap("DipoleMap2", "R");
fField->AddField(map_t);
fField->AddField(map_d1);
fField->AddField(map_d2);
PndConstField *fSolField=new PndConstField();
fSolField->SetField(0,0,20); // values are in kG //for cross-check with results from maps set Bz=2T
fSolField->SetFieldRegion(-240,240,-240,240,-172,283.7);//z range is sum from Solenoid#1-#4 maps
fField->AddField(fSolField);
fRun->SetField(fField);
The simulation with such fields set is running, but I see many messages:
GetBz Should be implimented
Does it mean that I didn't something wrong with constant mag. field?
Best regards,
Anastasia.
[Updated on: Mon, 01 July 2013 21:37] Report message to a moderator |
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| Re: Constant magnetic field instead Solenoid Field maps [message #14906 is a reply to message #14905] |
Tue, 02 July 2013 07:53  |
Ralf Kliemt
Messages: 507
Registered: May 2007
Location: GSI, Darmstadt
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first-grade participant |
From: *gsi.de
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Hello Anastasia,
The GetBz() function in FairField is not implemented. Please get your B Field like that (important are the double arrays):
double pnt[3]={0.,0.,0.}; //Position where to get field strength
double Bf[3]; //result goes here
// retrieve the field from the framework
FairRunAna::Instance()->GetField()->GetFieldValue ( pnt, Bf ); //[kGs]
return Bf[2]; //OK, Bf[2] is your Bz
Please mind the units.
In Analysis macros you can use RhoCalculationTools::GetBz(TVector3 pos).
Cheers.
Ralf
[Updated on: Tue, 02 July 2013 08:22] Report message to a moderator |
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| Re: Constant magnetic field instead Solenoid Field maps [message #14910 is a reply to message #14905] |
Tue, 02 July 2013 10:58 |
Anastasia Karavdina
Messages: 76
Registered: May 2010
Location: Mainz, Germany
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continuous participant |
From: *kph.uni-mainz.de
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Ok, the message "GetBz Should be implimented" is misleading since it's printed from GetBxyz method, which is indeed isn't implemented in PndConstField. Also it isn't implemented in PndFieldMap class, but there is no messages with maps fields usage.
Seems like this call happens in
void PndMultiField::GetFieldValue(const Double_t point[3], Double_t* bField)
{
PndRegion *fReg=0;
FairField *fField=0;
for (fMapIter=fFieldMaps.begin(); fMapIter!= fFieldMaps.end();fMapIter++ ){
fReg=fMapIter->first;
if(fReg->IsInside(point[2])){
fField=fMapIter->second;
break;
}
}
if(fField){
fField->GetBxyz(point, bField);
}else{
bField[0] = 0;
bField[1] = 0;
bField[2] = 0;
}
}
But if I understand this code correctly is should call GetBxyz for both PndConstField as well as PndFieldMap. Why there is no error messages when PndFieldMap is used?
[Updated on: Tue, 02 July 2013 11:10] Report message to a moderator |
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| Re: Constant magnetic field instead Solenoid Field maps [message #14911 is a reply to message #14905] |
Tue, 02 July 2013 11:43 |
Anastasia Karavdina
Messages: 76
Registered: May 2010
Location: Mainz, Germany
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continuous participant |
From: *kph.uni-mainz.de
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Well, I was wrong about GetBxyz method implementation in case field maps classes, actually it is implemented there.
For PndConstField I propose following implementation of this method (which is basicly merge of GetBx(), GetBy(),GetBz()):
void PndConstField::GetBxyz(const Double_t point[3], Double_t* bField){
if ( point [0] < fXmin || point [0] > fXmax ||
point [1] < fYmin || point [1] > fYmax ||
point [2] < fZmin || point [2] > fZmax ) {
bField[0]=0; bField[1]=0; bField[2]=0;
}
else{
bField[0]=fBx; bField[1]=fBy; bField[2]=fBz;
}
}
Can it be insert in svn version of code, please? Stefano, I can send changed source and header files if they needed.
Cheers,
Anastasia
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| Re: Constant magnetic field instead Solenoid Field maps [message #14917 is a reply to message #14911] |
Wed, 03 July 2013 09:37 |
Mohammad Al-Turany
Messages: 518
Registered: April 2004
Location: GSI, Germany
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first-grade participant |
From: *gsi.de
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Hallo,
let me try to explain you what is the problem here, before telling you that it is now completely solved in svn 20585!
The method GetFieldValue is called from VMC (simulation) so we have to keep the name and argument as they are. However some time one is interested in only one component of the field, that is why we implement the GetBx, GetBy and GetBz methods, now each of these methods check the boundary of the field map so when you need all of them it make no sense to check the same boundary three times, that is why we introduce the GetBxyz for the field maps but never for the constant field.
Now since Anastasia is mixing a constant field with maps this problem show up and exactly in the function PndMultiField::GetFieldValue as she find out, normally or till now we did not need to implement the GetBxyz for the constant field (we never have this use case), most of the people are using the scale of the field to change the whole map if needed, maybe this is also an option for you to test! you can simply use
void PndFieldMap::SetScale(Double_t factor)
This will scale the field map you use by this factor (all field components will be scaled for the map)
In any case one should also implement the function for GetBxyz for the const field also to solve the problem in your use case. This is all done now and I also change the output to have more meaningful warnings!
best regards,
Mohammad
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