PMT signal processor interface. More...

#include <JPMTSignalProcessorInterface.hh>

Inheritance diagram for JDETECTOR::JPMTSignalProcessorInterface:

Public Types
enum	JThresholdDomains { BELOW_THRESHOLDBAND = -1, IN_THRESHOLDBAND = 0, ABOVE_THRESHOLD = 2 }
	Threshold domain specifiers. More...

Public Member Functions
	JPMTSignalProcessorInterface (const double max_charge=100.0)
	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 in accordance with gain and gain spread. More...

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

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

virtual double	getRiseTime (const double npe) const
	Get time to pass 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 void	merge (JPMTData< JPMTPulse > &data) const
	Merging of PMT hits. More...

virtual double	getNPE (const double tot_ns, const double eps=1.0e-3) const
	Get number of photo-electrons. More...

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

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

Protected Attributes
double	MAX_CHARGE
	Maximum charge [npe]. More...

Private Attributes
JPMTData< JPhotoElectron >	buffer

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 JPMTSignalProcessorInterface::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. All photo-electrons are then time sorted. The photo-electrons which simultaneously arrive are merged. The corresponding condition is defined by member method JPMTSignalProcessorInterface::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. 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 JPMTSignalProcessorInterface::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 JPMTSignalProcessorInterface::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. The width of the charge distribution and the two photo-electron resolution are implemented in methods JPMTSignalProcessorInterface::getQmin() and JPMTSignalProcessorInterface::getTmin(), respectively. For a realistic PMT simulation, the derived class should provide for an implementation of each of these virtual methods.

Definition at line 69 of file JPMTSignalProcessorInterface.hh.

Member Enumeration Documentation

enum JDETECTOR::JPMTSignalProcessorInterface::JThresholdDomains

Threshold domain specifiers.

Enumerator
BELOW_THRESHOLDBAND	below threshold band
IN_THRESHOLDBAND	inside threshold band
ABOVE_THRESHOLD	above threshold band

Definition at line 89 of file JPMTSignalProcessorInterface.hh.

                            {
       BELOW_THRESHOLDBAND = -1,     //!< below  threshold band
       IN_THRESHOLDBAND    =  0,     //!< inside threshold band
       ABOVE_THRESHOLD     =  2      //!< above  threshold band
     };

Constructor & Destructor Documentation

JDETECTOR::JPMTSignalProcessorInterface::JPMTSignalProcessorInterface ( const double max_charge = 100.0 )

inline

Default constructor.

Definition at line 74 of file JPMTSignalProcessorInterface.hh.

                                                                   :
       MAX_CHARGE(max_charge)
     {}

virtual JDETECTOR::JPMTSignalProcessorInterface::~JPMTSignalProcessorInterface ( )

inlinevirtual

Virtual destructor.

Definition at line 82 of file JPMTSignalProcessorInterface.hh.

83 {}

Member Function Documentation

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

inline

Process hits.

Parameters

calibration	PMT calibration
input	PMT signals
output	PMT hits

Definition at line 103 of file JPMTSignalProcessorInterface.hh.

     {
       // apply transition time distribution to each photo-electron.
 
       buffer.clear();
       
       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) > BELOW_THRESHOLDBAND) {
             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 always true.

Returns: true

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 155 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 168 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.

Two (or more) photo-electrons are merged if they are comparable. The default implementation returns uses JPMTSignalProcessorInterface::getTmin() as time window.

Parameters

first	first photo-electron
second	second photo-electron

Returns: false

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 184 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 in accordance with 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 197 of file JPMTSignalProcessorInterface.hh.

     {
       return (double) NPE;
     }

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

inlinevirtual

Get probability 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 210 of file JPMTSignalProcessorInterface.hh.

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

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

inlinevirtual

Apply threshold.

The default implementation returns always ABOVE_THRESHOLD.

Parameters

npe	number of photo-electrons

Returns: threshold domain;

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 223 of file JPMTSignalProcessorInterface.hh.

     {
       return ABOVE_THRESHOLD;
     }

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

inlinevirtual

Get time to pass threshold.

The default implementation returns 0.

Parameters

npe	number of photo-electrons

Returns: time [ns]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 236 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 returns JPMTSignalProcessorInterface::getTmin().

Parameters

npe	number of photo-electrons

Returns: ToT [ns]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 249 of file JPMTSignalProcessorInterface.hh.

     {
       return getTmin();
     }

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

inlinevirtual

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

The default implementation returns infinity.

Parameters

npe	number of photo-electrons

Returns: dnpe/dToT [ns^-1]

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 262 of file JPMTSignalProcessorInterface.hh.

     {
       return std::numeric_limits<double>::max();
     }

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 275 of file JPMTSignalProcessorInterface.hh.

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

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

Definition at line 294 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));
     }

virtual double JDETECTOR::JPMTSignalProcessorInterface::getNPE	(	const double	tot_ns,
		const double	eps = `1.0e-3`
	)		const

inlinevirtual

Get number of photo-electrons.

The default implementation finds the time-over-threshold iteratively.

Parameters

tot_ns	time over threshold [ns]
eps	precision

Returns: number of photo-electrons

Reimplemented in JDETECTOR::JPMTAnalogueSignalProcessor.

Definition at line 327 of file JPMTSignalProcessorInterface.hh.

     {
       static const int N = 100;
 
       if (tot_ns > 0.0) {
 
         double xmin = 0.0;
         double xmax = MAX_CHARGE;
       
         for (int i = 0; i != N; ++i) {
         
           const double x = 0.5 * (xmin + xmax);
           const double y = this->getTimeOverThreshold(x);
 
           if (fabs(y - tot_ns) < eps) {
             return x;
           }
           
           if (y < tot_ns)
             xmin = x;
           else
             xmax = x;
         }
 
         return 0.5 * (xmin + xmax);
 
       } else {
 
         double xmin = 0.0;
         double xmax = 2.0;
       
         for (int i = 0; i != N; ++i) {
           
           const double x = 0.5 * (xmin + xmax);
           const double y = this->getTimeOverThreshold(x);
 
           if (y == 0.0)
             xmin = x;
           else
             xmax = x;
         }
 
         return 0.5 * (xmin + xmax);
       }
     }