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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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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 -----------------------------
200 #include <TTree.h> // ROOT_TTree
201 //#include <TRandom.h> // ROOT_TRandom
202 // #include <AliLog.h> // ALILOG_H
203 #include "AliFMDDebug.h" // Better debug macros
204 #include "AliFMDBaseDigitizer.h" // ALIFMDDIGITIZER_H
205 #include "AliFMD.h" // ALIFMD_H
206 #include "AliFMDGeometry.h" // ALIFMDGEOMETRY_H
207 #include "AliFMDDetector.h" // ALIFMDDETECTOR_H
208 #include "AliFMDRing.h" // ALIFMDRING_H
209 #include "AliFMDHit.h" // ALIFMDHIT_H
210 // #include "AliFMDDigit.h" // ALIFMDDIGIT_H
211 #include "AliFMDParameters.h" // ALIFMDPARAMETERS_H
212 // #include <AliRunDigitizer.h> // ALIRUNDIGITIZER_H
213 //#include <AliRun.h> // ALIRUN_H
214 #include <AliLoader.h> // ALILOADER_H
215 #include <AliRun.h> // ALILOADER_H
216 #include <AliRunLoader.h> // ALIRUNLOADER_H
219 //====================================================================
220 ClassImp(AliFMDBaseDigitizer)
222 ; // This is here to keep Emacs for indenting the next line
225 //____________________________________________________________________
226 AliFMDBaseDigitizer::AliFMDBaseDigitizer()
229 fEdep(AliFMDMap::kMaxDetectors,
230 AliFMDMap::kMaxRings,
231 AliFMDMap::kMaxSectors,
232 AliFMDMap::kMaxStrips),
234 fStoreTrackRefs(kTRUE)
236 AliFMDDebug(1, ("Constructed"));
237 // Default ctor - don't use it
240 //____________________________________________________________________
241 AliFMDBaseDigitizer::AliFMDBaseDigitizer(AliRunDigitizer* manager)
242 : AliDigitizer(manager, "AliFMDBaseDigitizer", "FMD Digitizer base class"),
245 fEdep(AliFMDMap::kMaxDetectors,
246 AliFMDMap::kMaxRings,
247 AliFMDMap::kMaxSectors,
248 AliFMDMap::kMaxStrips),
250 fStoreTrackRefs(kTRUE)
253 AliFMDDebug(1, ("Constructed"));
257 //____________________________________________________________________
258 AliFMDBaseDigitizer::AliFMDBaseDigitizer(const Char_t* name,
260 : AliDigitizer(name, title),
263 fEdep(AliFMDMap::kMaxDetectors,
264 AliFMDMap::kMaxRings,
265 AliFMDMap::kMaxSectors,
266 AliFMDMap::kMaxStrips),
268 fStoreTrackRefs(kTRUE)
271 AliFMDDebug(1, (" Constructed"));
275 //____________________________________________________________________
276 AliFMDBaseDigitizer::~AliFMDBaseDigitizer()
281 //____________________________________________________________________
283 AliFMDBaseDigitizer::Init()
285 // Initialization. Get a pointer to the parameter manager, and
287 AliFMDParameters::Instance()->Init();
288 if (AliLog::GetDebugLevel("FMD","") >= 15)
289 AliFMDParameters::Instance()->Print("");
293 //____________________________________________________________________
295 AliFMDBaseDigitizer::MakePedestal(UShort_t detector,
298 UShort_t strip) const
300 // Make a pedestal. The pedestal value is drawn from a Gaussian
301 // distribution. The mean of the distribution is the measured
302 // pedestal, and the width is the measured noise.
303 AliFMDParameters* param =AliFMDParameters::Instance();
304 Float_t mean =param->GetPedestal(detector,ring,sector,strip);
305 Float_t width =param->GetPedestalWidth(detector,ring,sector,strip);
306 return UShort_t(TMath::Max(gRandom->Gaus(mean, width), 0.));
309 //____________________________________________________________________
311 AliFMDBaseDigitizer::AddContribution(UShort_t detector,
320 // Add edep contribution from (detector,ring,sector,strip) to cache
321 AliFMDParameters* param = AliFMDParameters::Instance();
323 // Check if strip is `dead'
324 if (param->IsDead(detector, ring, sector, strip)) {
325 AliFMDDebug(5, ("FMD%d%c[%2d,%3d] is marked as dead",
326 detector, ring, sector, strip));
329 // Check if strip is out-side read-out range
330 // if (strip < minstrip || strip > maxstrip) {
331 // AliFMDDebug(5, ("FMD%d%c[%2d,%3d] is outside range [%3d,%3d]",
332 // detector,ring,sector,strip,minstrip,maxstrip));
336 AliFMDEdepHitPair& entry = fEdep(detector, ring, sector, strip);
338 // Give warning in case of double sdigit
339 if (entry.fEdep != 0)
340 AliFMDDebug(5, ("Double digit in FMD%d%c[%2d,%3d]",
341 detector, ring, sector, strip));
343 // Sum energy deposition
346 if (isPrimary) entry.fNPrim += nTrack;
347 if (fStoreTrackRefs) {
348 Int_t oldN = entry.fLabels.fN;
349 entry.fLabels.Set(entry.fN);
350 for (Int_t i = 0; i < nTrack; i++)
351 entry.fLabels[oldN + i] = tracknos[i];
353 AliFMDDebug(15, ("Adding contribution %f to FMD%d%c[%2d,%3d] (%f) track %d",
354 edep, detector, ring, sector, strip,
355 entry.fEdep, (nTrack > 0 ? tracknos[0] : -1)));
359 //____________________________________________________________________
361 AliFMDBaseDigitizer::DigitizeHits() const
363 // For the stored energy contributions in the cache (fEdep), convert
364 // the energy signal to ADC counts, and store the created digit in
365 // the digits array (AliFMD::fDigits)
367 AliFMDDebug(5, ("Will now digitize all the summed signals"));
368 AliFMDGeometry* geometry = AliFMDGeometry::Instance();
371 for (UShort_t detector=1; detector <= 3; detector++) {
372 AliFMDDebug(10, ("Processing hits in FMD%d", detector));
373 // Get pointer to subdetector
374 AliFMDDetector* det = geometry->GetDetector(detector);
376 for (UShort_t ringi = 0; ringi <= 1; ringi++) {
377 Char_t ring = ringi == 0 ? 'I' : 'O';
378 AliFMDDebug(10, (" Processing hits in FMD%d%c", detector,ring));
379 // Get pointer to Ring
380 AliFMDRing* r = det->GetRing(ring);
383 // Get number of sectors
384 UShort_t nSectors = UShort_t(360. / r->GetTheta());
385 // Loop over the number of sectors
386 for (UShort_t sector = 0; sector < nSectors; sector++) {
387 AliFMDDebug(10, (" Processing hits in FMD%d%c[%2d]",
388 detector,ring,sector));
389 // Get number of strips
390 UShort_t nStrips = r->GetNStrips();
391 // Loop over the stips
393 for (UShort_t strip = 0; strip < nStrips; strip++) {
394 // Reset the counter array to the invalid value -1
396 // Reset the last `ADC' value when we've get to the end of a
397 // VA1_ALICE channel.
398 if (strip % 128 == 0) last = 0;
400 const AliFMDEdepHitPair& entry = fEdep(detector,ring,sector,strip);
401 Float_t edep = entry.fEdep;
402 UShort_t ntot = entry.fN;
403 UShort_t nprim = entry.fNPrim;
404 const TArrayI& labels = entry.fLabels;
406 AliFMDDebug(15, ("Edep = %f for FMD%d%c[%2d,%3d]",
407 edep, detector, ring, sector, strip));
408 ConvertToCount(edep, last, detector, ring, sector, strip, counts);
412 // The following line was introduced - wrongly - by Peter
413 // Hristov. It _will_ break the digitisation and the
414 // following reconstruction. The behviour of the
415 // digitisation models exactly the front-end as it should
416 // (no matter what memory concuption it may entail). The
417 // check should be on zero suppression, since that's what
418 // models the front-end - if zero suppression is turned on
419 // in the front-end, then we can suppress empty digits -
420 // otherwise we shoud never do that. Note, that the line
421 // affects _both_ normal digitisation and digitisation for
422 // summable digits, since the condition is on the energy
423 // deposition and not on the actual number of counts. If
424 // this line should go anywhere, it should be in the
425 // possible overloaded AliFMDSDigitizer::AddDigit - not
428 // if (edep<=0) continue;
429 AddDigit(detector, ring, sector, strip, edep,
430 UShort_t(counts[0]), Short_t(counts[1]),
431 Short_t(counts[2]), Short_t(counts[3]),
432 ntot, nprim, labels);
433 AliFMDDebug(15, (" Adding digit in FMD%d%c[%2d,%3d]=%d",
434 detector,ring,sector,strip,counts[0]));
436 // This checks if the digit created will give the `right'
437 // number of particles when reconstructed, using a naiive
438 // approach. It's here only as a quality check - nothing
440 CheckDigit(digit, fEdep(detector, ring, sector, strip).fN,
449 //____________________________________________________________________
451 AliFMDBaseDigitizer::ConvertToCount(Float_t edep,
457 TArrayI& counts) const
459 // Convert the total energy deposited to a (set of) ADC count(s).
463 // Energy_Deposited ALTRO_Channel_Size
464 // ADC = -------------------------- ------------------- + pedestal
465 // Energy_Deposition_Of_1_MIP VA1_ALICE_MIP_Range
467 // Energy_Deposited fAltroChannelSize
468 // = --------------------------------- ----------------- + pedestal
469 // 1.664 * Si_Thickness * Si_Density fVA1MipRange
472 // = Energy_Deposited * ConversionFactor + pedestal
474 // However, this is modified by the response function of the
475 // VA1_ALICE pre-amp. chip in case we are doing oversampling of the
478 // In that case, we get N=fSampleRate values of the ADC, and the
479 // `EnergyDeposited' is a function of which sample where are
480 // calculating the ADC for
482 // ADC_i = f(EnergyDeposited, i/N, Last) * ConversionFactor + pedestal
484 // where Last is the Energy deposited in the previous strip.
486 // Here, f is the shaping function of the VA1_ALICE. This is given
489 // | (E - l) * (1 - exp(-B * t) + l if E > l
491 // | (l - E) * exp(-B * t) + E otherwise
494 // = E + (l - E) * ext(-B * t)
496 AliFMDParameters* param = AliFMDParameters::Instance();
497 Float_t convF = (param->GetDACPerMIP() / param->GetEdepMip() *
498 param->GetPulseGain(detector,ring,sector,strip));
499 Int_t ped = MakePedestal(detector,ring,sector,strip);
500 Int_t maxAdc = param->GetAltroChannelSize()-1;
502 AliWarning(Form("Maximum ADC is %d < 0, forcing it to 1023", maxAdc));
505 UShort_t rate = param->GetSampleRate(detector,ring,sector,strip);
506 AliFMDDebug(15, ("Sample rate for FMD%d%c[%2d,%3d] = %d",
507 detector, ring, sector, strip, rate));
508 if (rate < 1 || rate > 4) {
509 AliWarning(Form("Invalid sample rate for for FMD%d%c[%2d,%3d] = %d",
510 detector, ring, sector, strip, rate));
514 // In case we don't oversample, just return the end value.
516 Float_t a = edep * convF + ped;
518 counts[0] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
519 AliFMDDebug(15, ("FMD%d%c[%2d,%3d]: converting ELoss %f to "
521 detector,ring,sector,strip,edep,counts[0],convF,ped));
527 Float_t b = fShapingTime;
528 for (Ssiz_t i = 0; i < rate; i++) {
529 Float_t t = Float_t(i) / rate + 1./rate;
530 Float_t s = edep + (last - edep) * TMath::Exp(-b * t);
531 Float_t a = Int_t(s * convF + ped);
533 counts[i] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
535 AliFMDDebug(15, ("Converted edep = %f to ADC (%x,%x,%x,%x) "
536 "[gain: %f=(%f/%f*%f), pedestal: %d, rate: %d]",
537 edep, counts[0], counts[1], counts[2], counts[3],
538 convF, param->GetDACPerMIP(),param->GetEdepMip(),
539 param->GetPulseGain(detector,ring,sector,strip),
543 //____________________________________________________________________
545 AliFMDBaseDigitizer::AddDigit(UShort_t detector,
555 UShort_t /* nprim */,
556 const TArrayI& refs) const
558 // Add a digit or summable digit
560 fFMD->AddDigitByFields(detector, ring, sector, strip,
561 count1, count2, count3, count4, refs);
564 //____________________________________________________________________
566 AliFMDBaseDigitizer::MakeOutputTree(AliLoader* loader)
568 // Create output tree using loader. If the passed loader differs
569 // from the currently set loader in the FMD object, reset the FMD
570 // loader to be the passed loader. This is for the cases wher the
571 // output is different from the output.
572 AliFMDDebug(5, ("Making digits tree"));
573 loader->LoadDigits("UPDATE"); // "RECREATE");
574 TTree* out = loader->TreeD();
575 if (!out) loader->MakeTree("D");
576 out = loader->TreeD();
579 if (loader != fFMD->GetLoader())
580 fFMD->SetLoader(loader);
581 fFMD->MakeBranch("D");
586 //____________________________________________________________________
588 AliFMDBaseDigitizer::StoreDigits(AliLoader* loader)
590 // Write the digits to disk
591 AliFMDDebug(5, ("Storing %d digits", fFMD->Digits()->GetEntries()));
592 loader->WriteDigits("OVERWRITE");
593 loader->UnloadDigits();
594 // Reset the digits in the AliFMD object
598 //____________________________________________________________________