Index: /trunk/MagicSoft/Mars/Changelog =================================================================== --- /trunk/MagicSoft/Mars/Changelog (revision 3413) +++ /trunk/MagicSoft/Mars/Changelog (revision 3414) @@ -8,4 +8,5 @@ - fixed a little bug (exchanged a - with a + in the Calc() method) + 2004/03/05: Markus Gaug * mcalib/MCalibraitonChargeCalc.cc @@ -14,4 +15,5 @@ return kTRUE; which gave always true since this week, don't know why. + - added some information in class description Index: /trunk/MagicSoft/Mars/mcalib/MCalibrationChargeCalc.cc =================================================================== --- /trunk/MagicSoft/Mars/mcalib/MCalibrationChargeCalc.cc (revision 3413) +++ /trunk/MagicSoft/Mars/mcalib/MCalibrationChargeCalc.cc (revision 3414) @@ -34,30 +34,19 @@ // for every pixel. It is filled in the following way: // -// ProProcess: Search for MPedestalCam, MExtractedSignalCam and MExtractedSignalBlindPixel -// Initialize MCalibrationCam +// ProProcess: Initialize MCalibrationCam // Initialize pulser light wavelength // // ReInit: MCalibrationCam::InitSize(NumPixels) is called which allocates // memory in a TClonesArray of type MCalibrationChargePix -// Initialize number of used FADC slices -// Optionally exclude pixels from calibration -// -// Process: Every MCalibrationChargePix holds a histogram class, -// MHCalibrationPixel which itself hold histograms of type: -// HCharge(npix) (distribution of summed FADC time slice -// entries) -// HTime(npix) (distribution of position of maximum) -// HChargevsN(npix) (distribution of charges vs. event number. -// -// PostProcess: All histograms HCharge(npix) are fitted to a Gaussian -// All histograms HTime(npix) are fitted to a Gaussian -// The histogram HBlindPixelCharge (blind pixel) is fitted to -// a single PhE fit -// -// The histograms of the PIN Diode are fitted to Gaussians -// -// Fits can be excluded via the commands: -// MalibrationCam::SkipBlindPixelFits() (skip all blind -// pixel fits) +// +// Process: Nothing done by this class, histograms are filled by +// MHCalibrationChargeCam +// +// PstProcess: Fit results from MHCalibrationChargeCam are retrieved +// and used for the calculation of the reduced sigma, +// the F-Factor method, the blind pixel method (photon flux +// inside plexiglass) and +// the PINDiode method (photon flux +// outside plexiglass) // // Hi-Gain vs. Lo-Gain Calibration (very memory-intensive) @@ -68,10 +57,118 @@ // MRawEvtData // MPedestalCam -// MExtractedSignalCam -// MExtractedSignalBlindPixel +// MCalibrationCam // // Output Containers: // MCalibrationCam // +// +// Preliminary description of the calibration in photons (email from 12/02/04) +// +// Why calibrating in photons: +// =========================== +// +// At the Barcelona meeting in 2002, we decided to calibrate the camera in +// photons. This for the following reasons: +// +// * The physical quantity arriving at the camera are photons. This is +// the direct physical information from the air shower. The photons +// have a flux and a spectrum. +// +// * The photon fluxes depend mostly on the shower energy (with +// corrections deriving from the observation conditions), while the photon +// spectra depend mostly on the observation conditions: zenith angle, +// quality of the air, also the impact parameter of the shower. +// +// * The photomultiplier, in turn, has different response properties +// (quantum efficiencies) for photons of different colour. (Moreover, +// different pixels have slightly different quantum efficiencies). +// The resulting number of photo-electrons is then amplified (linearly) +// with respect to the photo-electron flux. +// +// * In the ideal case, one would like to disentagle the effects +// of the observation conditions from the primary particle energy (which +// one likes to measure). To do so, one needs: +// +// 1) A reliable calibration relating the FADC counts to the photo-electron +// flux -> This is accomplished with the F-Factor method. +// +// 2) A reliable calibration of the wavelength-dependent quantum efficiency +// -> This is accomplished with the combination of the three methods, +// together with QE-measurements performed by David in order to do +// the interpolation. +// +// 3) A reliable calibration of the observation conditions. This means: +// - Tracing the atmospheric conditions -> LIDAR +// - Tracing the observation zenith angle -> Drive System +// 4) Some knowlegde about the impact parameter: +// - This is the only part which cannot be accomplished well with a +// single telescope. We would thus need to convolute the spectrum +// over the distribution of impact parameters. +// +// +// How an ideal calibration would look like: +// ========================================= +// +// We know from the combined PIN-Diode and Blind-Pixel Method the response of +// each pixel to well-measured light fluxes in three representative +// wavelengths (green, blue, UV). We also know the response to these light +// fluxes in photo-electrons. Thus, we can derive: +// +// - conversion factors to photo-electrons +// - conversion factors to photons in three wavelengths. +// +// Together with David's measurements and some MC-simulation, we should be +// able to derive tables for typical Cherenkov-photon spectra - convoluted +// with the impact parameters and depending on the athmospheric conditions +// and the zenith angle (the "outer parameters"). +// +// From these tables we can create "calibration tables" containing some +// effective quantum efficiency depending on these outer parameters and which +// are different for each pixel. +// +// In an ideal MCalibrate, one would thus have to convert first the FADC +// slices to Photo-electrons and then, depending on the outer parameters, +// look up the effective quantum efficiency and get the mean number of +// photons which is then used for the further analysis. +// +// How the (first) MAGIC calibration should look like: +// =================================================== +// +// For the moment, we have only one reliable calibration method, although +// with very large systematic errors. This is the F-Factor method. Knowing +// that the light is uniform over the whole camera (which I would not at all +// guarantee in the case of the CT1 pulser), one could in principle already +// perform a relative calibration of the quantum efficiencies in the UV. +// However, the spread in QE at UV is about 10-15% (according to the plot +// that Abelardo sent around last time. The spread in photo-electrons is 15% +// for the inner pixels, but much larger (40%) for the outer ones. +// +// I'm not sure if we can already say that we have measured the relative +// difference in quantum efficiency for the inner pixels and produce a first +// QE-table for each pixel. To so, I would rather check in other wavelengths +// (which we can do in about one-two weeks when the optical transmission of +// the calibration trigger is installed). +// +// Thus, for the moment being, I would join Thomas proposal to calibrate in +// photo-electrons and apply one stupid average quantum efficiency for all +// pixels. This keeping in mind that we will have much preciser information +// in about one to two weeks. +// +// +// What MCalibrate should calculate and what should be stored: +// =========================================================== +// +// It is clear that in the end, MCerPhotEvt will store photons. +// MCalibrationCam stores the conversionfactors to photo-electrons and also +// some tables of how to apply the conversion to photons, given the outer +// parameters. This is not yet implemented and not even discussed. +// +// To start, I would suggest that we define the "average quantum efficiency" +// (maybe something like 25+-3%) and apply them equally to all +// photo-electrons. Later, this average factor can be easily replaced by a +// pixel-dependent factor and later by a (pixel-dependent) table. +// +// +// ////////////////////////////////////////////////////////////////////////////// #include "MCalibrationChargeCalc.h" @@ -399,5 +496,5 @@ *fLog << err << GetDescriptor() << ": Dear Michele! All pixels have non-valid calibration. " << "Did you forget to fill the histograms (filling MHCalibrationChargeCam from MExtractedSignalCam using MFillH) ? " << endl; - return kFALSE; + return kFALSE; } @@ -485,4 +582,4 @@ fCam->SetReadyToSave(); - return kTRUE; +return kTRUE; }