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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 -----------------------------
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 <AliRunLoader.h> // ALIRUNLOADER_H
217 //====================================================================
218 ClassImp(AliFMDBaseDigitizer)
220 ; // This is here to keep Emacs for indenting the next line
223 //____________________________________________________________________
224 AliFMDBaseDigitizer::AliFMDBaseDigitizer()
226 fEdep(AliFMDMap::kMaxDetectors,
227 AliFMDMap::kMaxRings,
228 AliFMDMap::kMaxSectors,
229 AliFMDMap::kMaxStrips),
232 // Default ctor - don't use it
235 //____________________________________________________________________
236 AliFMDBaseDigitizer::AliFMDBaseDigitizer(AliRunDigitizer* manager)
237 : AliDigitizer(manager, "AliFMDBaseDigitizer", "FMD Digitizer base class"),
239 fEdep(AliFMDMap::kMaxDetectors,
240 AliFMDMap::kMaxRings,
241 AliFMDMap::kMaxSectors,
242 AliFMDMap::kMaxStrips),
246 AliFMDDebug(1, (" processed"));
250 //____________________________________________________________________
251 AliFMDBaseDigitizer::AliFMDBaseDigitizer(const Char_t* name,
253 : AliDigitizer(name, title),
255 fEdep(AliFMDMap::kMaxDetectors,
256 AliFMDMap::kMaxRings,
257 AliFMDMap::kMaxSectors,
258 AliFMDMap::kMaxStrips)
261 AliFMDDebug(1, (" processed"));
265 //____________________________________________________________________
266 AliFMDBaseDigitizer::~AliFMDBaseDigitizer()
271 //____________________________________________________________________
273 AliFMDBaseDigitizer::Init()
276 AliFMDParameters::Instance()->Init();
281 //____________________________________________________________________
283 AliFMDBaseDigitizer::MakePedestal(UShort_t,
292 //____________________________________________________________________
294 AliFMDBaseDigitizer::SumContributions(AliFMD* fmd)
296 // Sum energy deposited contributions from each hit in a cache
299 Fatal("SumContributions", "no run loader");
301 // Clear array of deposited energies
304 // Get the FMD loader
305 AliLoader* inFMD = fRunLoader->GetLoader("FMDLoader");
307 inFMD->LoadHits("READ");
309 // Get the tree of hits
310 TTree* hitsTree = inFMD->TreeH();
313 inFMD->LoadHits("READ");
314 hitsTree = inFMD->TreeH();
317 // Get the FMD branch
318 TBranch* hitsBranch = hitsTree->GetBranch("FMD");
319 if (hitsBranch) fmd->SetHitsAddressBranch(hitsBranch);
320 else AliFatal("Branch FMD hit not found");
322 // Get a list of hits from the FMD manager
323 TClonesArray *fmdHits = fmd->Hits();
325 // Get number of entries in the tree
326 Int_t ntracks = Int_t(hitsTree->GetEntries());
328 AliFMDParameters* param = AliFMDParameters::Instance();
330 // Loop over the tracks in the
331 for (Int_t track = 0; track < ntracks; track++) {
332 // Read in entry number `track'
333 read += hitsBranch->GetEntry(track);
335 // Get the number of hits
336 Int_t nhits = fmdHits->GetEntries ();
337 for (Int_t hit = 0; hit < nhits; hit++) {
338 // Get the hit number `hit'
340 static_cast<AliFMDHit*>(fmdHits->UncheckedAt(hit));
342 // Extract parameters
343 UShort_t detector = fmdHit->Detector();
344 Char_t ring = fmdHit->Ring();
345 UShort_t sector = fmdHit->Sector();
346 UShort_t strip = fmdHit->Strip();
347 Float_t edep = fmdHit->Edep();
348 // UShort_t minstrip = param->GetMinStrip(detector, ring, sector, strip);
349 // UShort_t maxstrip = param->GetMaxStrip(detector, ring, sector, strip);
350 // Check if strip is `dead'
351 AliFMDDebug(2, ("Hit in FMD%d%c[%2d,%3d]=%f",
352 detector, ring, sector, strip, edep));
353 if (param->IsDead(detector, ring, sector, strip)) {
354 AliFMDDebug(1, ("FMD%d%c[%2d,%3d] is marked as dead",
355 detector, ring, sector, strip));
358 // Check if strip is out-side read-out range
359 // if (strip < minstrip || strip > maxstrip) {
360 // AliFMDDebug(5, ("FMD%d%c[%2d,%3d] is outside range [%3d,%3d]",
361 // detector,ring,sector,strip,minstrip,maxstrip));
365 // Give warning in case of double hit
366 if (fEdep(detector, ring, sector, strip).fEdep != 0)
367 AliFMDDebug(5, ("Double hit in %d%c(%d,%d)",
368 detector, ring, sector, strip));
370 // Sum energy deposition
371 fEdep(detector, ring, sector, strip).fEdep += edep;
372 fEdep(detector, ring, sector, strip).fN += 1;
373 // Add this to the energy deposited for this strip
376 AliFMDDebug(1, ("Size of cache: %d bytes, read %d bytes",
377 sizeof(fEdep), read));
380 //____________________________________________________________________
382 AliFMDBaseDigitizer::DigitizeHits(AliFMD* fmd) const
384 // For the stored energy contributions in the cache (fEdep), convert
385 // the energy signal to ADC counts, and store the created digit in
386 // the digits array (AliFMD::fDigits)
388 AliFMDGeometry* geometry = AliFMDGeometry::Instance();
391 for (UShort_t detector=1; detector <= 3; detector++) {
392 AliFMDDebug(5, ("Processing hits in FMD%d", detector));
393 // Get pointer to subdetector
394 AliFMDDetector* det = geometry->GetDetector(detector);
396 for (UShort_t ringi = 0; ringi <= 1; ringi++) {
397 Char_t ring = ringi == 0 ? 'I' : 'O';
398 AliFMDDebug(5, (" Processing hits in FMD%d%c", detector,ring));
399 // Get pointer to Ring
400 AliFMDRing* r = det->GetRing(ring);
403 // Get number of sectors
404 UShort_t nSectors = UShort_t(360. / r->GetTheta());
405 // Loop over the number of sectors
406 for (UShort_t sector = 0; sector < nSectors; sector++) {
407 AliFMDDebug(5, (" Processing hits in FMD%d%c[%2d]",
408 detector,ring,sector));
409 // Get number of strips
410 UShort_t nStrips = r->GetNStrips();
411 // Loop over the stips
413 for (UShort_t strip = 0; strip < nStrips; strip++) {
414 // Reset the counter array to the invalid value -1
416 // Reset the last `ADC' value when we've get to the end of a
417 // VA1_ALICE channel.
418 if (strip % 128 == 0) last = 0;
420 Float_t edep = fEdep(detector, ring, sector, strip).fEdep;
421 ConvertToCount(edep, last, detector, ring, sector, strip, counts);
423 AddDigit(fmd, detector, ring, sector, strip, edep,
424 UShort_t(counts[0]), Short_t(counts[1]),
425 Short_t(counts[2]), Short_t(counts[3]));
426 AliFMDDebug(10, (" Adding digit in FMD%d%c[%2d,%3d]=%d",
427 detector,ring,sector,strip,counts[0]));
429 // This checks if the digit created will give the `right'
430 // number of particles when reconstructed, using a naiive
431 // approach. It's here only as a quality check - nothing
433 CheckDigit(digit, fEdep(detector, ring, sector, strip).fN,
442 //____________________________________________________________________
444 AliFMDBaseDigitizer::ConvertToCount(Float_t edep,
450 TArrayI& counts) const
452 // Convert the total energy deposited to a (set of) ADC count(s).
456 // Energy_Deposited ALTRO_Channel_Size
457 // ADC = -------------------------- ------------------- + pedestal
458 // Energy_Deposition_Of_1_MIP VA1_ALICE_MIP_Range
460 // Energy_Deposited fAltroChannelSize
461 // = --------------------------------- ----------------- + pedestal
462 // 1.664 * Si_Thickness * Si_Density fVA1MipRange
465 // = Energy_Deposited * ConversionFactor + pedestal
467 // However, this is modified by the response function of the
468 // VA1_ALICE pre-amp. chip in case we are doing oversampling of the
471 // In that case, we get N=fSampleRate values of the ADC, and the
472 // `EnergyDeposited' is a function of which sample where are
473 // calculating the ADC for
475 // ADC_i = f(EnergyDeposited, i/N, Last) * ConversionFactor + pedestal
477 // where Last is the Energy deposited in the previous strip.
479 // Here, f is the shaping function of the VA1_ALICE. This is given
482 // | (E - l) * (1 - exp(-B * t) + l if E > l
484 // | (l - E) * exp(-B * t) + E otherwise
487 // = E + (l - E) * ext(-B * t)
489 AliFMDParameters* param = AliFMDParameters::Instance();
490 Float_t convF = 1./param->GetPulseGain(detector,ring,sector,strip);
491 Int_t ped = MakePedestal(detector,ring,sector,strip);
492 Int_t maxAdc = param->GetAltroChannelSize()-1;
494 AliWarning(Form("Maximum ADC is %d < 0, forcing it to 1023", maxAdc));
497 UShort_t rate = param->GetSampleRate(detector,ring,sector,strip);
498 if (rate < 1 || rate > 4) rate = 1;
500 // In case we don't oversample, just return the end value.
502 Float_t a = edep * convF + ped;
504 counts[0] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
505 AliFMDDebug(2, ("FMD%d%c[%2d,%3d]: converting ELoss %f to "
507 detector,ring,sector,strip,edep,counts[0],convF,ped));
512 Float_t b = fShapingTime;
513 for (Ssiz_t i = 0; i < rate; i++) {
514 Float_t t = Float_t(i) / rate + 1./rate;
515 Float_t s = edep + (last - edep) * TMath::Exp(-b * t);
516 Float_t a = Int_t(s * convF + ped);
518 counts[i] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
524 //____________________________________________________________________