Coding conventions (Christian)
[u/mrichter/AliRoot.git] / FMD / AliFMDBaseDigitizer.h
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02a27b50 1#ifndef ALIFMDBASEDIGITIZER_H
2#define ALIFMDBASEDIGITIZER_H
3/* Copyright(c) 1998-2000, ALICE Experiment at CERN, All rights
4 * reserved.
5 *
6 * See cxx source for full Copyright notice
7 */
8// Classses to make Hits into digits and summable digits.
9//
10// Digits consists of
11// - Detector #
12// - Ring ID
13// - Sector #
14// - Strip #
15// - ADC count in this channel
16//
17// Summable digits consists of
18// - Detector #
19// - Ring ID
20// - Sector #
21// - Strip #
22// - Total energy deposited in the strip
23// - ADC count in this channel
24//
25/** @file AliFMDBaseDigitizer.h
26 @author Christian Holm Christensen <cholm@nbi.dk>
27 @date Mon Mar 27 12:38:26 2006
28 @brief FMD Digitizers declaration
29 @ingroup FMD_sim
30*/
31#ifndef ALIDIGITIZER_H
32# include <AliDigitizer.h>
33#endif
34#ifndef ALIRUNDIGITIZER_H
35# include <AliRunDigitizer.h>
36#endif
37#ifndef ALIFMDEdepMAP_H
38# include "AliFMDEdepMap.h"
39#endif
40//====================================================================
41class TClonesArray;
42class AliFMD;
43class AliLoader;
44class AliRunLoader;
45class AliFMDDigit;
46
47
48//====================================================================
49/** @class AliFMDBaseDigitizer AliFMDDigitizer.h <FMD/AliFMDDigitizer>
50 @brief Base class for digitizers.
51
52 This class contains the procedures simulation ADC signal for the
53 Forward Multiplicity detector : Hits->Digits and Hits->SDigits
54
55 Digits consists of
56 - Detector #
57 - Ring ID
58 - Sector #
59 - Strip #
60 - ADC count in this channel
61
62 Summable digits consists of
63 - Detector #
64 - Ring ID
65 - Sector #
66 - Strip #
67 - Total energy deposited in the strip
68 - ADC count in this channel
69
70 As the Digits and SDigits have so much in common, the classes
71 AliFMDDigitizer and AliFMDSDigitizer are implemented via a base
72 class AliFMDBaseDigitizer.
73 @verbatim
74 +---------------------+
75 | AliFMDBaseDigitizer |
76 +---------------------+
77 ^
78 |
79 +----------+---------+
80 | |
81 +-----------------+ +------------------+
82 | AliFMDDigitizer | | AliFMDSDigitizer |
83 +-----------------+ +------------------+
84 @endverbatim
85 These classes uses parameters fetched from the AliFMDParameters
86 manager.
87
88 The shaping function of the VA1 is generally given by
89 @f[
90 f(x) = A(1 - \exp(-Bx))
91 @f]
92 where A is the total charge collected in the pre-amp., and B is a
93 paramter that depends on the shaping time of the VA1 circut.
94
95 When simulating the shaping function of the VA1 pre-amp. chip, we
96 have to take into account, that the shaping function depends on
97 the previous value of read from the pre-amp.
98
99 That results in the following algorithm:
100 @code
101 last = 0;
102 for (i=0; i < n_pre_amp_charge; i++) {
103 charge = GetCharge(i);
104 if (last < charge)
105 f(t) = (charge - last) * (1 - exp(-B * t)) + last
106 else
107 f(t) = (last - charge) * exp(-B * t) + charge)
108 for (j=0; j < sample_rate; j++)
109 adc[j] = f(i / (# samples))
110 last = charge
111 }
112 @endcode
113 Here, the first loop is over all charges collected by the VA1
114 chip, and the @c sample_rate is how many times the ALTRO ADC
115 samples each of the 128 charges from the pre-amp.
116
117 The @c charge is the total charge @f$ Q@f$ collected by the VA1
118 pre-amplifier for a strip. @f$ Q@f$ is then given by
119 @f[
120 Q = \frac{E}{e}\frac{S}{r}
121 @f]
122 where @f$ E@f$ is the total energy deposited in a silicon strip,
123 @f$ R@f$ is the dynamic range of the VA1 pre-amp, @f$ e@f$ is the
124 energy deposited by a single MIP, and @f$ S@f$ ALTRO channel size
125 in each time step.
126
127 The energy deposited per MIP is given by
128 @f$
129 e = M \rho w
130 @f$
131 where @f$ M@f$ is the universal number
132 @f$ 1.664 \mbox{keV}\mbox{cm}^{2}\mbox{g}^{-1}@f$, @f$ \rho@f$ is
133 the density of silicon, and @f$ w@f$ is the depth of the silicon
134 sensor.
135
136 The final ADC count is given by
137 @f[
138 C' = C + P
139 @f]
140 where @f$ P@f$ is the (randomized) pedestal.
141
142 This class uses the class template AliFMDEdepMap to make an
143 internal cache of the energy deposted of the hits. The class
144 template is instantasized as
145
146 The first member of the values is the summed energy deposition in a
147 given strip, while the second member of the values is the number of
148 hits in a given strip. Using the second member, it's possible to
149 do some checks on just how many times a strip got hit, and what
150 kind of error we get in our reconstructed hits. Note, that this
151 information is currently not written to the digits tree. I think a
152 QA (Quality Assurance) digit tree is better suited for that task.
153 However, the information is there to be used in the future.
154 @ingroup FMD_sim
155 */
156class AliFMDBaseDigitizer : public AliDigitizer
157{
158public:
159 /** CTOR */
160 AliFMDBaseDigitizer();
161 /** Normal CTOR
162 @param manager Manager of digitization */
163 AliFMDBaseDigitizer(AliRunDigitizer * manager);
164 /** Normal ctor
165 @param name Name
166 @param title Title */
167 AliFMDBaseDigitizer(const Char_t* name, const Char_t* title);
168 /** DTOR */
169 virtual ~AliFMDBaseDigitizer();
170
171 /** Initialize */
172 virtual Bool_t Init();
173
174 /** The response shape of the VA1 shaping circuit is approximently
175 given by
176 @f[
177 f(x) = A(1 - \exp(-Bx))
178 @f]
179 where @f$ A@f$ is the total charge collected by the pre-amp.,
180 and @f$ B@f$ is parameter that depends on the shaping time of
181 the @b VA1 pre-amp. This member function sets the parameter @f$
182 B@f$
183 @param B */
184 void SetShapingTime(Float_t B=10) { fShapingTime = B; }
185 /** @return Get the shaping time */
186 Float_t GetShapingTime() const { return fShapingTime; }
187protected:
188 /** Sum energy deposited contributions from each hit in a cache
189 @param fmd Pointer to detector */
190 virtual void SumContributions(AliFMD* fmd);
191 /** For the stored energy contributions in the cache, convert the
192 energy signal to ADC counts, and store the created digit in
193 the digits array
194 @param fmd Pointer to detector */
195 virtual void DigitizeHits(AliFMD* fmd) const;
196 /** Convert the total energy deposited to a (set of) ADC count(s).
197 See also the class description for more details.
198 @param edep Total energy deposited in detector
199 @param last Last charge collected in previous VA1 channnel
200 @param detector Detector #
201 @param ring Ring ID
202 @param sector Sector #
203 @param strip Strip #
204 @param counts Array holding the counts on return */
205 virtual void ConvertToCount(Float_t edep,
206 Float_t last,
207 UShort_t detector,
208 Char_t ring,
209 UShort_t sector,
210 UShort_t strip,
211 TArrayI& counts) const;
212 /** Make a pedestal
213 @param detector Detector #
214 @param ring Ring ID
215 @param sector Sector #
216 @param strip Strip #
217 @return Pedestal value */
218 virtual UShort_t MakePedestal(UShort_t detector,
219 Char_t ring,
220 UShort_t sector,
221 UShort_t strip) const;
222 /** Add noise to each sample */
223 virtual void AddNoise(TArrayI&) const {}
224 /** Add a digit to output */
225 virtual void AddDigit(AliFMD* /* fmd */,
226 UShort_t /* detector */,
227 Char_t /* ring */,
228 UShort_t /* sector */,
229 UShort_t /* strip */,
230 Float_t /* edep */,
231 UShort_t /* count1 */,
232 Short_t /* count2 */,
233 Short_t /* count3 */) const {}
234
235 AliRunLoader* fRunLoader; //! Run loader
236 AliFMDEdepMap fEdep; // Cache of Energy from hits
237 Float_t fShapingTime; // Shaping profile parameter
238
239 /** Copy CTOR
240 @param o object to copy from */
241 AliFMDBaseDigitizer(const AliFMDBaseDigitizer& o)
242 : AliDigitizer(o) {}
243 /** Assignment operator
244 @return Reference to this object */
245 AliFMDBaseDigitizer& operator=(const AliFMDBaseDigitizer&) { return *this; }
246 ClassDef(AliFMDBaseDigitizer,2) // Base class for FMD digitizers
247};
248
249
250#endif
251//____________________________________________________________________
252//
253// Local Variables:
254// mode: C++
255// End:
256//
257//
258// EOF
259//
260