PMT signal processor interface. More...

#include <JPMTSignalProcessorInterface.hh>

Inheritance diagram for JDETECTOR::JPMTSignalProcessorInterface:

Public Member Functions
	JPMTSignalProcessorInterface ()
	Default constructor. More...

virtual	~JPMTSignalProcessorInterface ()
	Virtual destructor. More...

void	operator() (const JCalibration &calibration, const JPMTData< JPMTSignal > &input, JPMTData< JPMTPulse > &output) const
	Process hits. More...

virtual bool	applyQE () const
	Apply relative QE. More...

virtual double	getRandomTime (const double t_ns) const
	Get randomised time according transition time distribution. More...

virtual bool	compare (const JPhotoElectron &first, const JPhotoElectron &second) const
	Compare arrival times of photo-electrons. More...

virtual double	getRandomCharge (const int NPE) const
	Get randomised charge according to gain and gain spread. More...

virtual double	getChargeProbability (const double npe, const int NPE) const
	Get probability density for given charge. More...

virtual bool	applyThreshold (const double npe) const
	Apply threshold. More...

virtual double	getRiseTime (const double npe) const
	Get time to reach threshold. More...

virtual double	getTimeOverThreshold (const double npe) const
	Get time-over-threshold (ToT). More...

virtual double	getDerivative (const double npe) const
	Get derivative of number of photo-electrons to time-over-threshold. More...

virtual double	getSurvivalProbability (const int NPE) const
	Probability that a hit survives the simulation of the PMT. More...

virtual double	getNPE (const double tot_ns) const
	Get number of photo-electrons. More...

virtual void	merge (JPMTData< JPMTPulse > &data) const
	Merging of PMT hits. More...

Static Public Member Functions
static double	getTmin ()
	Get two photo-electron resolution for time-over-threshold. More...

static double	getQmin ()
	Get width of charge distribution. More...

Detailed Description

PMT signal processor interface.

This class supports the implementation of the PMT simulator interface using an alternative set of virtual methods. These methods constitute a user interface to the expected performance of a PMT.

Each photon is converted to a photo-electron using member method getRandomTime(). For this, the data structure JPhotoElectron is used. Note that the quantum efficiency (QE) of the PMT actually is included in the simulation of the detector response. A relative QE is applied via method applyQE(). All photo-electrons are then time sorted. The photo-electrons which simultaneously arrive are merged. The corresponding condition is defined by member method compare(). The time of the combined signal is determined by the time of the first photo-electron and the rise time of the analogue pulse to the threshold of the discriminator via method getRiseTime(). In this, the actual amplitude of the combined analogue signal and the calibration of the PMT are taken into account. The amplitude of the combined analogue signal is simulated using member method getRandomCharge(). For this, the data structure JPMTSignal is used.

The analogue signals of the PMT are processed by a discriminator. This discriminator produces a time-over-threshold signal for each analogue signal that passes a preset threshold. The output signal is described by the time of the leading edge and the length of the time-over-threshold signal. For this, the data structure JPMTPulse is used. The determination of the time of the leading edge and the length of the time-over-threshold signal require a designated model. The class JPMTAnalogueSignalProcessor provides for an implementation of such a model.

Overlapping time-over-threshold pulses are merged. The time of the leading edge is then set to the earliest leading edge and the time-over-threshold to the difference between the latest trailing edge and the earliest leading edge. The merging of hits is implemented in member method merge().

The default implementation of these virtual methods corresponds to no smearing and a time-over-threshold value equal to a fixed two photo-electron resolution times the number of photo-electrons. The width of the charge distribution and the two photo-electron resolution are implemented in methods getQmin() and getTmin(), respectively.

For a realistic PMT simulation, the derived class should provide for an implementation of each of these virtual methods.

Definition at line 63 of file JPMTSignalProcessorInterface.hh.

Constructor & Destructor Documentation

JDETECTOR::JPMTSignalProcessorInterface::JPMTSignalProcessorInterface ( )

inline

Default constructor.

Definition at line 68 of file JPMTSignalProcessorInterface.hh.

69 {}

virtual JDETECTOR::JPMTSignalProcessorInterface::~JPMTSignalProcessorInterface ( )

inlinevirtual

Virtual destructor.

Definition at line 75 of file JPMTSignalProcessorInterface.hh.

76 {}

Member Function Documentation

void JDETECTOR::JPMTSignalProcessorInterface::operator()	(	const JCalibration &	calibration,
		const JPMTData< JPMTSignal > &	input,
		JPMTData< JPMTPulse > &	output
	)		const

inline

Process hits.

Two (or more) photo-electrons are combined if they are comparable according method compare.
Two (or more) consecutive hits hits maybe merged (according method merge).

Parameters

calibration	PMT calibration
input	PMT signals
output	PMT hits

Definition at line 89 of file JPMTSignalProcessorInterface.hh.

     {
       // apply transition time distribution to each photo-electron.
 
       JPMTData<JPhotoElectron> buffer;
       
       for (JPMTData<JPMTSignal>::const_iterator hit = input.begin(); hit != input.end(); ++hit) {
 
         for (int i = 0; i != hit->npe; ++i) {
 
           if (applyQE()) {
             buffer.push_back(JPhotoElectron(getRandomTime(hit->t_ns)));
           }
         }
       }
 
       if (!buffer.empty()) {
       
         buffer.push_back(JPhotoElectron::getEndMarker());
       
         buffer.sort();
       
       
         // generate PMT hits from time sequence of photo-electrons.
         
         for (JPMTData<JPhotoElectron>::const_iterator q = buffer.begin(), p = q++; q != buffer.end(); ++q) {
           
           while (compare(*p,*q)) {
             ++q;
           }
           
           const double npe = getRandomCharge(distance(p,q));
 
           if (applyThreshold(npe)) {
             output.push_back(JPMTPulse(putTime(p->t_ns + getRiseTime(npe), calibration), getTimeOverThreshold(npe)));
           }
 
           p = q;
         }
         
         // merge overlapping PMT hits.
       
         merge(output);
       }
     }

virtual bool JDETECTOR::JPMTSignalProcessorInterface::applyQE ( ) const

inlinevirtual

Apply relative QE.

The default implementation returns true.

Returns: true if accepted; false if rejected

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 144 of file JPMTSignalProcessorInterface.hh.

     {
       return true;
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getRandomTime ( const double t_ns ) const

inlinevirtual

Get randomised time according transition time distribution.

The default implementation returns the given value.

Parameters

t_ns time [ns]

Returns: time [ns]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 157 of file JPMTSignalProcessorInterface.hh.

     {
       return t_ns;
     }

virtual bool JDETECTOR::JPMTSignalProcessorInterface::compare	(	const JPhotoElectron &	first,
		const JPhotoElectron &	second
	)		const

inlinevirtual

Compare arrival times of photo-electrons.

The default implementation uses method getTmin as two photo-electron resolution.

Parameters

first	first photo-electron
second	second photo-electron

Returns: true if arrival times of photo-electrons are within two photo-electron resolution; else false

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 171 of file JPMTSignalProcessorInterface.hh.

     {
       return second.t_ns - first.t_ns <= getTmin();
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getRandomCharge ( const int NPE ) const

inlinevirtual

Get randomised charge according to gain and gain spread.

The default implementation returns the given value.

Parameters

NPE	number of photo-electrons

Returns: number of photo-electrons

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 184 of file JPMTSignalProcessorInterface.hh.

     {
       return (double) NPE;
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getChargeProbability	(	const double	npe,
		const int	NPE
	)		const

inlinevirtual

Get probability density for given charge.

Parameters

npe	observed number of photo-electrons
NPE	true number of photo-electrons

Returns: probability [npe^-1]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 197 of file JPMTSignalProcessorInterface.hh.

     {
       return (fabs(npe - NPE) <= 0.5 * getQmin() ? 1.0 / getQmin() : 0.0);
     }

virtual bool JDETECTOR::JPMTSignalProcessorInterface::applyThreshold ( const double npe ) const

inlinevirtual

Apply threshold.

The default implementation returns true.

Parameters

npe	number of photo-electrons

Returns: true if pass; else false

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 210 of file JPMTSignalProcessorInterface.hh.

     {
       return (npe > 0.0);
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getRiseTime ( const double npe ) const

inlinevirtual

Get time to reach threshold.

The default implementation returns 0.

Parameters

npe	number of photo-electrons

Returns: time [ns]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 223 of file JPMTSignalProcessorInterface.hh.

     {
       return 0.0;
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getTimeOverThreshold ( const double npe ) const

inlinevirtual

Get time-over-threshold (ToT).

The default implementation corresponds to a linear relation between the number of photo-electrons and the time-over-threshold.

Parameters

npe	number of photo-electrons

Returns: ToT [ns]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 236 of file JPMTSignalProcessorInterface.hh.

     {
       return TIME_OVER_THRESHOLD_NS  +  getTmin() * (round(npe) - 1.0);
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getDerivative ( const double npe ) const

inlinevirtual

Get derivative of number of photo-electrons to time-over-threshold.

Parameters

npe	number of photo-electrons

Returns: dnpe/dToT [ns^-1]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 248 of file JPMTSignalProcessorInterface.hh.

     {
       return 1.0 / getTmin();
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getSurvivalProbability ( const int NPE ) const

inlinevirtual

Probability that a hit survives the simulation of the PMT.

The default implementation returns 1 if given value larger than 0.

Parameters

NPE	number of photo-electrons

Returns: probability

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 261 of file JPMTSignalProcessorInterface.hh.

     {
       if (NPE > 0)
         return 1.0;
       else
         return 0.0;
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getNPE ( const double tot_ns ) const

inlinevirtual

Get number of photo-electrons.

The default implementation corresponds to a linear relation between the number of photo-electrons and the time-over-threshold.

Parameters

tot_ns time over threshold [ns]

Returns: number of photo-electrons

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 277 of file JPMTSignalProcessorInterface.hh.

     {
       return 1.0  +  (tot_ns - TIME_OVER_THRESHOLD_NS) / getTmin();
     }

virtual void JDETECTOR::JPMTSignalProcessorInterface::merge ( JPMTData< JPMTPulse > & data ) const

inlinevirtual

Merging of PMT hits.

Hits with overlapping time-over-threshold signals should -de facto- be combined. In this, the leading edge is maintained and the time-over-threshold is set to the difference between the overall trailing and leading edges. As a result, the number of PMT hits may be reduced.

Parameters

data	PMT hits (I/O)

Definition at line 293 of file JPMTSignalProcessorInterface.hh.

     {
       using namespace std;
       
       JPMTData<JPMTPulse>::iterator out = data.begin();
       
       for (JPMTData<JPMTPulse>::iterator i = data.begin(); i != data.end(); ) {
         
         double t1 = i->t_ns;
         double t2 = i->t_ns + i->tot_ns;
         
         while (++i != data.end() && i->t_ns < t2 + getTmin()) {
           t2 = max(t2, i->t_ns + i->tot_ns);
         }
         
         out->t_ns   = t1;
         out->tot_ns = t2 - t1;
         
         ++out;
       }
       
       data.resize(distance(data.begin(), out));
     }