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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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14 **************************************************************************/
16 /** @file AliFMDBaseDigitizer.cxx
17 @author Christian Holm Christensen <cholm@nbi.dk>
18 @date Mon Mar 27 12:38:26 2006
19 @brief FMD Digitizers implementation
22 //////////////////////////////////////////////////////////////////////////////
24 // This class contains the procedures simulation ADC signal for the
25 // Forward Multiplicity detector : Hits->Digits and Hits->SDigits
32 // - ADC count in this channel
39 // - Total energy deposited in the strip
40 // - ADC count in this channel
42 // As the Digits and SDigits have so much in common, the classes
43 // AliFMDDigitizer and AliFMDSDigitizer are implemented via a base
44 // class AliFMDBaseDigitizer.
46 // +---------------------+
47 // | AliFMDBaseDigitizer |
48 // +---------------------+
51 // +----------+---------+
53 // +-----------------+ +------------------+
54 // | AliFMDDigitizer | | AliFMDSDigitizer |
55 // +-----------------+ +------------------+
57 // These classes has several paramters:
61 // (Only AliFMDDigitizer)
62 // Mean and width of the pedestal. The pedestal is simulated
63 // by a Guassian, but derived classes my override MakePedestal
64 // to simulate it differently (or pick it up from a database).
67 // The dymamic MIP range of the VA1_ALICE pre-amplifier chip
70 // The largest number plus one that can be stored in one
71 // channel in one time step in the ALTRO ADC chip.
74 // How many times the ALTRO ADC chip samples the VA1_ALICE
75 // pre-amplifier signal. The VA1_ALICE chip is read-out at
76 // 10MHz, while it's possible to drive the ALTRO chip at
77 // 25MHz. That means, that the ALTRO chip can have time to
78 // sample each VA1_ALICE signal up to 2 times. Although it's
79 // not certain this feature will be used in the production,
80 // we'd like have the option, and so it should be reflected in
84 // The shaping function of the VA1_ALICE is generally given by
86 // f(x) = A(1 - exp(-Bx))
88 // where A is the total charge collected in the pre-amp., and B is a
89 // paramter that depends on the shaping time of the VA1_ALICE circut.
91 // When simulating the shaping function of the VA1_ALICe
92 // pre-amp. chip, we have to take into account, that the shaping
93 // function depends on the previous value of read from the pre-amp.
95 // That results in the following algorithm:
98 // FOR charge IN pre-amp. charge train DO
99 // IF last < charge THEN
100 // f(t) = (charge - last) * (1 - exp(-B * t)) + last
102 // f(t) = (last - charge) * exp(-B * t) + charge)
104 // FOR i IN # samples DO
105 // adc_i = f(i / (# samples))
112 // pre-amp. charge train
113 // is a series of 128 charges read from the VA1_ALICE chip
116 // is the number of times the ALTRO ADC samples each of the 128
117 // charges from the pre-amp.
119 // Where Q is the total charge collected by the VA1_ALICE
120 // pre-amplifier. Q is then given by
126 // where E is the total energy deposited in a silicon strip, R is the
127 // dynamic range of the VA1_ALICE pre-amp (fVA1MipRange), e is the
128 // energy deposited by a single MIP, and S ALTRO channel size in each
129 // time step (fAltroChannelSize).
131 // The energy deposited per MIP is given by
135 // where M is the universal number 1.664, rho is the density of
136 // silicon, and w is the depth of the silicon sensor.
138 // The final ADC count is given by
142 // where P is the (randomized) pedestal (see MakePedestal)
144 // This class uses the class template AliFMDMap<Type> to make an
145 // internal cache of the energy deposted of the hits. The class
146 // template is instantasized as
148 // typedef AliFMDMap<std::pair<Float_t, UShort_t> > AliFMDEdepMap;
150 // The first member of the values is the summed energy deposition in a
151 // given strip, while the second member of the values is the number of
152 // hits in a given strip. Using the second member, it's possible to
153 // do some checks on just how many times a strip got hit, and what
154 // kind of error we get in our reconstructed hits. Note, that this
155 // information is currently not written to the digits tree. I think a
156 // QA (Quality Assurance) digit tree is better suited for that task.
157 // However, the information is there to be used in the future.
160 // Latest changes by Christian Holm Christensen
162 //////////////////////////////////////////////////////////////////////////////
165 // | A(-1 + B + exp(-B))
166 // | f(x) dx = ------------------- = 1
170 // and B is the a parameter defined by the shaping time (fShapingTime).
172 // Solving the above equation, for A gives
175 // A = ----------------
178 // So, if we define the function g: [0,1] -> [0:1] by
181 // | Bu + exp(-Bu) - Bv - exp(-Bv)
182 // g(u,v) = | f(x) dx = -A -----------------------------
186 // we can evaluate the ALTRO sample of the VA1_ALICE pre-amp between
187 // any two times (u, v), by
190 // B Bu + exp(-Bu) - Bv - exp(-Bv)
191 // C = Q g(u,v) = - Q ---------------- -----------------------------
192 // -1 + B + exp(-B) B
194 // Bu + exp(-Bu) - Bv - exp(-Bv)
195 // = - Q -----------------------------
199 #include <TTree.h> // ROOT_TTree
200 //#include <TRandom.h> // ROOT_TRandom
201 #include <AliLog.h> // ALILOG_H
202 #include "AliFMDBaseDigitizer.h" // ALIFMDDIGITIZER_H
203 #include "AliFMD.h" // ALIFMD_H
204 #include "AliFMDGeometry.h" // ALIFMDGEOMETRY_H
205 #include "AliFMDDetector.h" // ALIFMDDETECTOR_H
206 #include "AliFMDRing.h" // ALIFMDRING_H
207 #include "AliFMDHit.h" // ALIFMDHIT_H
208 // #include "AliFMDDigit.h" // ALIFMDDIGIT_H
209 #include "AliFMDParameters.h" // ALIFMDPARAMETERS_H
210 // #include <AliRunDigitizer.h> // ALIRUNDIGITIZER_H
211 //#include <AliRun.h> // ALIRUN_H
212 #include <AliLoader.h> // ALILOADER_H
213 #include <AliRunLoader.h> // ALIRUNLOADER_H
215 //====================================================================
216 ClassImp(AliFMDBaseDigitizer)
218 ; // This is here to keep Emacs for indenting the next line
221 //____________________________________________________________________
222 AliFMDBaseDigitizer::AliFMDBaseDigitizer()
224 fEdep(AliFMDMap::kMaxDetectors,
225 AliFMDMap::kMaxRings,
226 AliFMDMap::kMaxSectors,
227 AliFMDMap::kMaxStrips),
230 // Default ctor - don't use it
233 //____________________________________________________________________
234 AliFMDBaseDigitizer::AliFMDBaseDigitizer(AliRunDigitizer* manager)
235 : AliDigitizer(manager, "AliFMDBaseDigitizer", "FMD Digitizer base class"),
237 fEdep(AliFMDMap::kMaxDetectors,
238 AliFMDMap::kMaxRings,
239 AliFMDMap::kMaxSectors,
240 AliFMDMap::kMaxStrips),
244 AliDebug(1," processed");
248 //____________________________________________________________________
249 AliFMDBaseDigitizer::AliFMDBaseDigitizer(const Char_t* name,
251 : AliDigitizer(name, title),
253 fEdep(AliFMDMap::kMaxDetectors,
254 AliFMDMap::kMaxRings,
255 AliFMDMap::kMaxSectors,
256 AliFMDMap::kMaxStrips)
259 AliDebug(1," processed");
263 //____________________________________________________________________
264 AliFMDBaseDigitizer::~AliFMDBaseDigitizer()
269 //____________________________________________________________________
271 AliFMDBaseDigitizer::Init()
274 AliFMDParameters::Instance()->Init();
279 //____________________________________________________________________
281 AliFMDBaseDigitizer::MakePedestal(UShort_t,
290 //____________________________________________________________________
292 AliFMDBaseDigitizer::SumContributions(AliFMD* fmd)
294 // Sum energy deposited contributions from each hit in a cache
297 Fatal("SumContributions", "no run loader");
299 // Clear array of deposited energies
302 // Get the FMD loader
303 AliLoader* inFMD = fRunLoader->GetLoader("FMDLoader");
305 inFMD->LoadHits("READ");
307 // Get the tree of hits
308 TTree* hitsTree = inFMD->TreeH();
311 inFMD->LoadHits("READ");
312 hitsTree = inFMD->TreeH();
315 // Get the FMD branch
316 TBranch* hitsBranch = hitsTree->GetBranch("FMD");
317 if (hitsBranch) fmd->SetHitsAddressBranch(hitsBranch);
318 else AliFatal("Branch FMD hit not found");
320 // Get a list of hits from the FMD manager
321 TClonesArray *fmdHits = fmd->Hits();
323 // Get number of entries in the tree
324 Int_t ntracks = Int_t(hitsTree->GetEntries());
326 AliFMDParameters* param = AliFMDParameters::Instance();
328 // Loop over the tracks in the
329 for (Int_t track = 0; track < ntracks; track++) {
330 // Read in entry number `track'
331 read += hitsBranch->GetEntry(track);
333 // Get the number of hits
334 Int_t nhits = fmdHits->GetEntries ();
335 for (Int_t hit = 0; hit < nhits; hit++) {
336 // Get the hit number `hit'
338 static_cast<AliFMDHit*>(fmdHits->UncheckedAt(hit));
340 // Extract parameters
341 UShort_t detector = fmdHit->Detector();
342 Char_t ring = fmdHit->Ring();
343 UShort_t sector = fmdHit->Sector();
344 UShort_t strip = fmdHit->Strip();
345 Float_t edep = fmdHit->Edep();
346 // UShort_t minstrip = param->GetMinStrip(detector, ring, sector, strip);
347 // UShort_t maxstrip = param->GetMaxStrip(detector, ring, sector, strip);
348 // Check if strip is `dead'
349 if (param->IsDead(detector, ring, sector, strip)) {
350 AliDebug(5, Form("FMD%d%c[%2d,%3d] is marked as dead",
351 detector, ring, sector, strip));
354 // Check if strip is out-side read-out range
355 // if (strip < minstrip || strip > maxstrip) {
356 // AliDebug(5, Form("FMD%d%c[%2d,%3d] is outside range [%3d,%3d]",
357 // detector,ring,sector,strip,minstrip,maxstrip));
361 // Give warning in case of double hit
362 if (fEdep(detector, ring, sector, strip).fEdep != 0)
363 AliDebug(5, Form("Double hit in %d%c(%d,%d)",
364 detector, ring, sector, strip));
366 // Sum energy deposition
367 fEdep(detector, ring, sector, strip).fEdep += edep;
368 fEdep(detector, ring, sector, strip).fN += 1;
369 // Add this to the energy deposited for this strip
372 AliDebug(1, Form("Size of cache: %d bytes, read %d bytes",
373 sizeof(fEdep), read));
376 //____________________________________________________________________
378 AliFMDBaseDigitizer::DigitizeHits(AliFMD* fmd) const
380 // For the stored energy contributions in the cache (fEdep), convert
381 // the energy signal to ADC counts, and store the created digit in
382 // the digits array (AliFMD::fDigits)
384 AliFMDGeometry* geometry = AliFMDGeometry::Instance();
387 for (UShort_t detector=1; detector <= 3; detector++) {
388 // Get pointer to subdetector
389 AliFMDDetector* det = geometry->GetDetector(detector);
391 for (UShort_t ringi = 0; ringi <= 1; ringi++) {
392 Char_t ring = ringi == 0 ? 'I' : 'O';
393 // Get pointer to Ring
394 AliFMDRing* r = det->GetRing(ring);
397 // Get number of sectors
398 UShort_t nSectors = UShort_t(360. / r->GetTheta());
399 // Loop over the number of sectors
400 for (UShort_t sector = 0; sector < nSectors; sector++) {
401 // Get number of strips
402 UShort_t nStrips = r->GetNStrips();
403 // Loop over the stips
405 for (UShort_t strip = 0; strip < nStrips; strip++) {
406 // Reset the counter array to the invalid value -1
408 // Reset the last `ADC' value when we've get to the end of a
409 // VA1_ALICE channel.
410 if (strip % 128 == 0) last = 0;
412 Float_t edep = fEdep(detector, ring, sector, strip).fEdep;
413 ConvertToCount(edep, last, detector, ring, sector, strip, counts);
415 AddDigit(fmd, detector, ring, sector, strip, edep,
416 UShort_t(counts[0]), Short_t(counts[1]),
419 // This checks if the digit created will give the `right'
420 // number of particles when reconstructed, using a naiive
421 // approach. It's here only as a quality check - nothing
423 CheckDigit(digit, fEdep(detector, ring, sector, strip).fN,
432 //____________________________________________________________________
434 AliFMDBaseDigitizer::ConvertToCount(Float_t edep,
440 TArrayI& counts) const
442 // Convert the total energy deposited to a (set of) ADC count(s).
446 // Energy_Deposited ALTRO_Channel_Size
447 // ADC = -------------------------- ------------------- + pedestal
448 // Energy_Deposition_Of_1_MIP VA1_ALICE_MIP_Range
450 // Energy_Deposited fAltroChannelSize
451 // = --------------------------------- ----------------- + pedestal
452 // 1.664 * Si_Thickness * Si_Density fVA1MipRange
455 // = Energy_Deposited * ConversionFactor + pedestal
457 // However, this is modified by the response function of the
458 // VA1_ALICE pre-amp. chip in case we are doing oversampling of the
461 // In that case, we get N=fSampleRate values of the ADC, and the
462 // `EnergyDeposited' is a function of which sample where are
463 // calculating the ADC for
465 // ADC_i = f(EnergyDeposited, i/N, Last) * ConversionFactor + pedestal
467 // where Last is the Energy deposited in the previous strip.
469 // Here, f is the shaping function of the VA1_ALICE. This is given
472 // | (E - l) * (1 - exp(-B * t) + l if E > l
474 // | (l - E) * exp(-B * t) + E otherwise
477 // = E + (l - E) * ext(-B * t)
479 AliFMDParameters* param = AliFMDParameters::Instance();
480 Float_t convF = 1/param->GetPulseGain(detector,ring,sector,strip);
481 UShort_t ped = MakePedestal(detector,ring,sector,strip);
482 UInt_t maxAdc = param->GetAltroChannelSize()-1;
483 UShort_t rate = param->GetSampleRate(detector,ring,sector,strip);
485 // In case we don't oversample, just return the end value.
487 counts[0] = UShort_t(TMath::Min(edep * convF + ped, Float_t(maxAdc)));
488 AliDebug(2, Form("FMD%d%c[%2d,%3d]: converting ELoss %f to ADC %d (%f)",
489 detector,ring,sector,strip,edep,counts[0],convF));
494 Float_t b = fShapingTime;
495 for (Ssiz_t i = 0; i < rate; i++) {
496 Float_t t = Float_t(i) / rate;
497 Float_t s = edep + (last - edep) * TMath::Exp(-b * t);
498 counts[i] = UShort_t(TMath::Min(s * convF + ped, Float_t(maxAdc)));
504 //____________________________________________________________________