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[u/mrichter/AliRoot.git] / FMD / AliFMDBaseDigitizer.cxx
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02a27b50 1/**************************************************************************
2 * Copyright(c) 2004, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
15/* $Id$ */
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
20 @ingroup FMD_sim
21*/
22//////////////////////////////////////////////////////////////////////////////
23//
24// This class contains the procedures simulation ADC signal for the
25// Forward Multiplicity detector : Hits->Digits and Hits->SDigits
26//
27// Digits consists of
28// - Detector #
29// - Ring ID
30// - Sector #
31// - Strip #
32// - ADC count in this channel
33//
34// Digits consists of
35// - Detector #
36// - Ring ID
37// - Sector #
38// - Strip #
39// - Total energy deposited in the strip
40// - ADC count in this channel
41//
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.
45//
46// +---------------------+
47// | AliFMDBaseDigitizer |
48// +---------------------+
49// ^
50// |
51// +----------+---------+
52// | |
53// +-----------------+ +------------------+
54// | AliFMDDigitizer | | AliFMDSDigitizer |
55// +-----------------+ +------------------+
56//
57// These classes has several paramters:
58//
59// fPedestal
60// fPedestalWidth
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).
65//
66// fVA1MipRange
67// The dymamic MIP range of the VA1_ALICE pre-amplifier chip
68//
69// fAltroChannelSize
70// The largest number plus one that can be stored in one
71// channel in one time step in the ALTRO ADC chip.
72//
73// fSampleRate
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
81// the code.
82//
83//
84// The shaping function of the VA1_ALICE is generally given by
85//
86// f(x) = A(1 - exp(-Bx))
87//
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.
90//
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.
94//
95// That results in the following algorithm:
96//
97// last = 0;
98// FOR charge IN pre-amp. charge train DO
99// IF last < charge THEN
100// f(t) = (charge - last) * (1 - exp(-B * t)) + last
101// ELSE
102// f(t) = (last - charge) * exp(-B * t) + charge)
103// ENDIF
104// FOR i IN # samples DO
105// adc_i = f(i / (# samples))
106// DONE
107// last = charge
108// DONE
109//
110// Here,
111//
112// pre-amp. charge train
113// is a series of 128 charges read from the VA1_ALICE chip
114//
115// # samples
116// is the number of times the ALTRO ADC samples each of the 128
117// charges from the pre-amp.
118//
119// Where Q is the total charge collected by the VA1_ALICE
120// pre-amplifier. Q is then given by
121//
122// E S
123// Q = - -
124// e R
125//
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).
130//
131// The energy deposited per MIP is given by
132//
133// e = M * rho * w
134//
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.
137//
138// The final ADC count is given by
139//
140// C' = C + P
141//
142// where P is the (randomized) pedestal (see MakePedestal)
143//
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
147//
148// typedef AliFMDMap<std::pair<Float_t, UShort_t> > AliFMDEdepMap;
149//
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.
158//
159//
160// Latest changes by Christian Holm Christensen
161//
162//////////////////////////////////////////////////////////////////////////////
163
164// /1
165// | A(-1 + B + exp(-B))
166// | f(x) dx = ------------------- = 1
167// | B
168// / 0
169//
170// and B is the a parameter defined by the shaping time (fShapingTime).
171//
172// Solving the above equation, for A gives
173//
174// B
175// A = ----------------
176// -1 + B + exp(-B)
177//
178// So, if we define the function g: [0,1] -> [0:1] by
179//
180// / v
181// | Bu + exp(-Bu) - Bv - exp(-Bv)
182// g(u,v) = | f(x) dx = -A -----------------------------
183// | B
184// / u
185//
186// we can evaluate the ALTRO sample of the VA1_ALICE pre-amp between
187// any two times (u, v), by
188//
189//
190// B Bu + exp(-Bu) - Bv - exp(-Bv)
191// C = Q g(u,v) = - Q ---------------- -----------------------------
192// -1 + B + exp(-B) B
193//
194// Bu + exp(-Bu) - Bv - exp(-Bv)
195// = - Q -----------------------------
196// -1 + B + exp(-B)
197//
198
090026bf 199#include <TMath.h>
02a27b50 200#include <TTree.h> // ROOT_TTree
201//#include <TRandom.h> // ROOT_TRandom
f95a63c4 202// #include <AliLog.h> // ALILOG_H
203#include "AliFMDDebug.h" // Better debug macros
02a27b50 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
6169f936 210// #include "AliFMDDigit.h" // ALIFMDDIGIT_H
02a27b50 211#include "AliFMDParameters.h" // ALIFMDPARAMETERS_H
6169f936 212// #include <AliRunDigitizer.h> // ALIRUNDIGITIZER_H
02a27b50 213//#include <AliRun.h> // ALIRUN_H
214#include <AliLoader.h> // ALILOADER_H
215#include <AliRunLoader.h> // ALIRUNLOADER_H
216
217//====================================================================
218ClassImp(AliFMDBaseDigitizer)
219#if 0
220 ; // This is here to keep Emacs for indenting the next line
221#endif
222
223//____________________________________________________________________
224AliFMDBaseDigitizer::AliFMDBaseDigitizer()
b5ee4425 225 : fRunLoader(0),
226 fEdep(AliFMDMap::kMaxDetectors,
227 AliFMDMap::kMaxRings,
228 AliFMDMap::kMaxSectors,
229 AliFMDMap::kMaxStrips),
2aeec17d 230 fShapingTime(6)
02a27b50 231{
232 // Default ctor - don't use it
233}
234
235//____________________________________________________________________
236AliFMDBaseDigitizer::AliFMDBaseDigitizer(AliRunDigitizer* manager)
237 : AliDigitizer(manager, "AliFMDBaseDigitizer", "FMD Digitizer base class"),
238 fRunLoader(0),
239 fEdep(AliFMDMap::kMaxDetectors,
240 AliFMDMap::kMaxRings,
241 AliFMDMap::kMaxSectors,
b5ee4425 242 AliFMDMap::kMaxStrips),
2aeec17d 243 fShapingTime(6)
02a27b50 244{
245 // Normal CTOR
f95a63c4 246 AliFMDDebug(1, (" processed"));
02a27b50 247 SetShapingTime();
248}
249
250//____________________________________________________________________
251AliFMDBaseDigitizer::AliFMDBaseDigitizer(const Char_t* name,
252 const Char_t* title)
253 : AliDigitizer(name, title),
254 fRunLoader(0),
255 fEdep(AliFMDMap::kMaxDetectors,
256 AliFMDMap::kMaxRings,
257 AliFMDMap::kMaxSectors,
258 AliFMDMap::kMaxStrips)
259{
260 // Normal CTOR
f95a63c4 261 AliFMDDebug(1, (" processed"));
02a27b50 262 SetShapingTime();
263}
264
265//____________________________________________________________________
266AliFMDBaseDigitizer::~AliFMDBaseDigitizer()
267{
268 // Destructor
269}
270
271//____________________________________________________________________
272Bool_t
273AliFMDBaseDigitizer::Init()
274{
275 // Initialization
276 AliFMDParameters::Instance()->Init();
277 return kTRUE;
278}
279
280
281//____________________________________________________________________
282UShort_t
283AliFMDBaseDigitizer::MakePedestal(UShort_t,
284 Char_t,
285 UShort_t,
286 UShort_t) const
287{
288 // Make a pedestal
289 return 0;
290}
291
292//____________________________________________________________________
293void
294AliFMDBaseDigitizer::SumContributions(AliFMD* fmd)
295{
296 // Sum energy deposited contributions from each hit in a cache
297 // (fEdep).
298 if (!fRunLoader)
299 Fatal("SumContributions", "no run loader");
300
301 // Clear array of deposited energies
302 fEdep.Reset();
303
304 // Get the FMD loader
305 AliLoader* inFMD = fRunLoader->GetLoader("FMDLoader");
306 // And load the hits
307 inFMD->LoadHits("READ");
308
309 // Get the tree of hits
310 TTree* hitsTree = inFMD->TreeH();
311 if (!hitsTree) {
312 // Try again
313 inFMD->LoadHits("READ");
314 hitsTree = inFMD->TreeH();
315 }
316
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");
321
322 // Get a list of hits from the FMD manager
323 TClonesArray *fmdHits = fmd->Hits();
324
325 // Get number of entries in the tree
326 Int_t ntracks = Int_t(hitsTree->GetEntries());
327
328 AliFMDParameters* param = AliFMDParameters::Instance();
329 Int_t read = 0;
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);
334
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'
339 AliFMDHit* fmdHit =
340 static_cast<AliFMDHit*>(fmdHits->UncheckedAt(hit));
341
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();
15b17c89 348 // UShort_t minstrip = param->GetMinStrip(detector, ring, sector, strip);
349 // UShort_t maxstrip = param->GetMaxStrip(detector, ring, sector, strip);
02a27b50 350 // Check if strip is `dead'
f95a63c4 351 AliFMDDebug(2, ("Hit in FMD%d%c[%2d,%3d]=%f",
352 detector, ring, sector, strip, edep));
02a27b50 353 if (param->IsDead(detector, ring, sector, strip)) {
f95a63c4 354 AliFMDDebug(1, ("FMD%d%c[%2d,%3d] is marked as dead",
02a27b50 355 detector, ring, sector, strip));
356 continue;
357 }
358 // Check if strip is out-side read-out range
15b17c89 359 // if (strip < minstrip || strip > maxstrip) {
f95a63c4 360 // AliFMDDebug(5, ("FMD%d%c[%2d,%3d] is outside range [%3d,%3d]",
15b17c89 361 // detector,ring,sector,strip,minstrip,maxstrip));
362 // continue;
363 // }
02a27b50 364
365 // Give warning in case of double hit
366 if (fEdep(detector, ring, sector, strip).fEdep != 0)
f95a63c4 367 AliFMDDebug(5, ("Double hit in %d%c(%d,%d)",
02a27b50 368 detector, ring, sector, strip));
369
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
374 } // hit loop
375 } // track loop
f95a63c4 376 AliFMDDebug(1, ("Size of cache: %d bytes, read %d bytes",
02a27b50 377 sizeof(fEdep), read));
378}
379
380//____________________________________________________________________
381void
382AliFMDBaseDigitizer::DigitizeHits(AliFMD* fmd) const
383{
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)
387 //
388 AliFMDGeometry* geometry = AliFMDGeometry::Instance();
389
2aeec17d 390 TArrayI counts(4);
02a27b50 391 for (UShort_t detector=1; detector <= 3; detector++) {
f95a63c4 392 AliFMDDebug(5, ("Processing hits in FMD%d", detector));
02a27b50 393 // Get pointer to subdetector
394 AliFMDDetector* det = geometry->GetDetector(detector);
395 if (!det) continue;
396 for (UShort_t ringi = 0; ringi <= 1; ringi++) {
397 Char_t ring = ringi == 0 ? 'I' : 'O';
f95a63c4 398 AliFMDDebug(5, (" Processing hits in FMD%d%c", detector,ring));
02a27b50 399 // Get pointer to Ring
400 AliFMDRing* r = det->GetRing(ring);
401 if (!r) continue;
402
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++) {
f95a63c4 407 AliFMDDebug(5, (" Processing hits in FMD%d%c[%2d]",
408 detector,ring,sector));
02a27b50 409 // Get number of strips
410 UShort_t nStrips = r->GetNStrips();
411 // Loop over the stips
412 Float_t last = 0;
413 for (UShort_t strip = 0; strip < nStrips; strip++) {
414 // Reset the counter array to the invalid value -1
415 counts.Reset(-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;
419
420 Float_t edep = fEdep(detector, ring, sector, strip).fEdep;
421 ConvertToCount(edep, last, detector, ring, sector, strip, counts);
422 last = edep;
423 AddDigit(fmd, detector, ring, sector, strip, edep,
424 UShort_t(counts[0]), Short_t(counts[1]),
2aeec17d 425 Short_t(counts[2]), Short_t(counts[3]));
f95a63c4 426 AliFMDDebug(10, (" Adding digit in FMD%d%c[%2d,%3d]=%d",
427 detector,ring,sector,strip,counts[0]));
02a27b50 428#if 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
432 // else.
433 CheckDigit(digit, fEdep(detector, ring, sector, strip).fN,
434 counts);
435#endif
436 } // Strip
437 } // Sector
438 } // Ring
439 } // Detector
440}
441
442//____________________________________________________________________
443void
444AliFMDBaseDigitizer::ConvertToCount(Float_t edep,
445 Float_t last,
446 UShort_t detector,
447 Char_t ring,
448 UShort_t sector,
449 UShort_t strip,
450 TArrayI& counts) const
451{
452 // Convert the total energy deposited to a (set of) ADC count(s).
453 //
454 // This is done by
455 //
456 // Energy_Deposited ALTRO_Channel_Size
457 // ADC = -------------------------- ------------------- + pedestal
458 // Energy_Deposition_Of_1_MIP VA1_ALICE_MIP_Range
459 //
460 // Energy_Deposited fAltroChannelSize
461 // = --------------------------------- ----------------- + pedestal
462 // 1.664 * Si_Thickness * Si_Density fVA1MipRange
463 //
464 //
465 // = Energy_Deposited * ConversionFactor + pedestal
466 //
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
469 // VA1_ALICE output.
470 //
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
474 //
475 // ADC_i = f(EnergyDeposited, i/N, Last) * ConversionFactor + pedestal
476 //
477 // where Last is the Energy deposited in the previous strip.
478 //
479 // Here, f is the shaping function of the VA1_ALICE. This is given
480 // by
481 //
482 // | (E - l) * (1 - exp(-B * t) + l if E > l
483 // f(E, t, l) = <
484 // | (l - E) * exp(-B * t) + E otherwise
485 //
486 //
487 // = E + (l - E) * ext(-B * t)
488 //
489 AliFMDParameters* param = AliFMDParameters::Instance();
a9579262 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;
493 if (maxAdc < 0) {
494 AliWarning(Form("Maximum ADC is %d < 0, forcing it to 1023", maxAdc));
495 maxAdc = 1023;
496 }
02a27b50 497 UShort_t rate = param->GetSampleRate(detector,ring,sector,strip);
2aeec17d 498 if (rate < 1 || rate > 4) rate = 1;
02a27b50 499
500 // In case we don't oversample, just return the end value.
501 if (rate == 1) {
a9579262 502 Float_t a = edep * convF + ped;
503 if (a < 0) a = 0;
504 counts[0] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
f95a63c4 505 AliFMDDebug(2, ("FMD%d%c[%2d,%3d]: converting ELoss %f to "
a9579262 506 "ADC %4d (%f,%d)",
507 detector,ring,sector,strip,edep,counts[0],convF,ped));
02a27b50 508 return;
509 }
510
511 // Create a pedestal
512 Float_t b = fShapingTime;
513 for (Ssiz_t i = 0; i < rate; i++) {
2aeec17d 514 Float_t t = Float_t(i) / rate + 1./rate;
a9579262 515 Float_t s = edep + (last - edep) * TMath::Exp(-b * t);
516 Float_t a = Int_t(s * convF + ped);
517 if (a < 0) a = 0;
518 counts[i] = UShort_t(TMath::Min(a, Float_t(maxAdc)));
02a27b50 519 }
520}
521
522
523
524//____________________________________________________________________
525//
526// EOF
527//
528
529
530
531