Authors:

G. De Cataldo (1), A. Di Mauro (2), A. Franco (3), P. Martinengo(2), V. Rizzi (3), A. Tauro (4)

(1)

CERN CH 1211 Geveve 23 and INFN sez. Bari, Italy

(2)

CERN CH 1211 Geneva 23

(3)

INFN sez. Bari, Italy

(4)

Politecnico di Bari and INFN sez. Bari, Italy

Abstract:

The aim of this report is to provide feedback on the use of the ALICE Detector Construction Data Base (DCDB) with the HMPID project as end-user. We have exploited the DCDB to store construction information and test results of the Front-End Electronics (FEE) cards. These results, obtained using a dedicated test bench, were automatically downloaded in the DCDB by means of a LabVIEW application. First, the test bench set-up is shortly described and the definition of the relevant FEE card parameters is given. Then we introduce the Dictionary Wizard to define the database fields for the HMPID FEE cards and finally a short description of the central DCDB Web Interface is also provided.

Contact person: G. De Cataldo

1. Introduction

The ALICE Detector Construction Database (DCDB) [1][2] contains the information about all the components required for assembling the single sub-detectors and ALICE itself. It includes the interconnecting components as trigger cables, shared crate, racks..etc. In this paper we will focus first on the HMPID [3] satellite DCDB [4] then we will provide some details on the already installed central ALICE DCDB [5], where some sub-detector DCDBs are already present.

2. The test bench, the FEE card parameters and the DCDB-LabVIEW interface.

The FEE card houses three GASSIPLEX chips, with 16 analogue channels each, for a total of 48 channels/card. For the HMPID project 3500 cards need to be tested. The relevant test parameters to be recorded are :

1. pedestal average value;
2. standard deviation of the pedestal distribution;
3. pedestal Min value;
4. pedestal Max value;
1. delta pedestal (Max-Min).
2. For the following measurement a known charge is injected at each input:
5. signal average value;
6. standard deviation of the signal distribution;
7. signal Min value;
8. signal Max value;
9. delta signal (Max –Min).

The test setup is based on a LeCroy LC 564A digital oscilloscope connected via the GPIB port to the PCI/GPIB interface of a PC. A dedicated LabVIEW application [6] collects and automatically stores the data on a second PC running the HMPID satellite DCDB. NIM modules provide the required control signals to the FEE card (track/hold, clock, clear, analog input test signal and event trigger). The test is carried out in two steps: during the first one the average pedestal value of the 48 channels is measured using 25 overlapped waveforms, each waveform consists of 20.000 samples (~10Ksamples /Gassiplex channel). In the second step a probe signal is injected via a capacitive fan-out of 5.6 pF/channel (±0.25 pF) to verify the amplifier responses and evaluate the gain spread between the channels. The amplitude of the test signal can be adjusted by means of a potentiometer. The results of the measurement, as well as the corresponding waveforms, are then presented to the operator and, after acceptance, downloaded in the HMPID satellite DCDB. Only the parameter’s values are saved but the waveforms. Fig.1 shows the LabVIEW application user interface. In the dashed rectangle there are the pedestal values calculated by the oscilloscope software, while in the dot-dashed rectangle are reported the GASSIPLEX IDs of the card under test. In Bari, for each GASSIPLEX ID are available on a PostgreSQL DB the results of the single chip test before its assembling on the boards. The merging of the two DBs in a unique HMPIH DCDB is under way.

Figure 1. This panel shows the graphic user interface (GUI) of the LabVIEW application. The 48 FEE channel profile during the multiplexing is shown in the oscilloscope dump, while the average pedestal value and other measured parameters, are reported in the dashed rectangle.

The parameter values calculated by the oscilloscope software when the test signal is injected in the FEE card are shown in the dashed rectangle in the figure 2. The resulting 48-channel profile produced during the multiplexing can also be seen on the oscilloscope screen dump. In order to let the operator to correct possible typing errors, the DCDB verifies that the ‘Local ID’ number, which unambiguously identifies the FEE card, is not already present in the database. In the present LabView application the same control is extended neither at the ‘ID card number’ (so far provided equal to the Local ID number), nor at the ‘Gassiplex chip ID’.

However the implementation of improved software is under way. An estimate of the GASSIPLEX gain spread, at ¼ of the dynamic range, is reported in Appendix A. In the worst case it is found to be less than 2.2 %.

Fig.2 Response of the 48 GASSISPLEX channels in the FEE card when a test signal is injected. If there are no noisy events affecting the calculation of the parameter values then the operator can download the test result in the HMPID satellite DCDB. If not the case the operator can restart the test.

3. The DCDB Dictionary Wizard

The DCDB Dictionary Wizard is a software tool helping the user in the definition of the database fields and their hierarchy, which contains all the relevant information about the detector components and the assembling sequences. In fig. 3 the black arrow shows the link from the main DCDB web page to the Dictionary Wizard.

The defined fields, as Components, processes, sub-processes, etc, can be arranged in “Compositions” according to the desired hierarchy. Fig. 4 shows a series of Components defined for the HMPID with the help of the DCDB experts [7], along with one Composition for the FEE card housing three GASSIPLEX chips. The hierarchical tree of this composition is also shown in fig. 5. For this test the component and process naming has partially followed the prescription in [8]. In the final version of the HMPID DCDB the proposed naming convention in [8] will be fully applied.

Figure 3.The DCDB homepage with the link to the Dictionary Wizard.

Figure 4. In the upper part of the figure are shown only some HMPID Components among all the possible, namely: the HMP-Module, the DILOGIC, the GASSIPLEX, the FECARD, the radiator components, etc. In the lower part it is shown the “Composition” between the Gassiplex analogue chips and the FEE card housing the gassiplex’s.

Figure 5. The hierarchical tree of the FEE card and GASSIPLEX composition is shown. It is a familiar way to represent to the user, at a glance, the DCDB structure.

Some aspects about the different detector composition trees that could be built on the same component list need to be still analyzed. As an example: the HMPID C6F14 Liquid

Circulation System (LCS) in principle could be partially traced via the components (header tubes, pressure sensors, radiators…) belonging to the seven HMPID modules in the corresponding composition tree. However, for the detector maintenance, the operator may need to have the view of the entire LCS including pumping station, filters, tanks, etc…. There are then some components that have to belong to both the different hierarchies: the HMPID-modules and the LCS. Although it seems to us that both the trees can be defined with the Dictionary Wizard, it is not evident if the addition or the removal of any component (detector design changing) must be notified to all the related composition trees or once done it propagates automatically to all the concerned hierarchies in the DCDB. In fig. 6 are shown the Processes defined for the HMPID (with Dictionary Wizard) containing the measured pedestal values of the FEE cards.

Figure 6. This figure shows all the Processes related to the FEE card and defined via the Dictionary Wizard. They contain all the test results for one FEE card.

The Central ALICE DCDB Web Interface

The central ALICE DCDB is supposed to contain a copy of all the sub-detector satellite DCDBs along with all the components needed for their integration in ALICE. Fig. 7 shows the central DCDB web page where in the sub-detector list there is also the Integration that will contain all the components not belonging to a specific sub-detector but requested for their integration in the experiment. Fig. 8 shows for the HMPID a list of components with the name HMP_GASSIPLEX073FEE-CARD and different ID. For each of them on the right side four different icons provide information about the related Processes and hierarchies.

Figure 7. After the Logon, this figure shows the central ALICE DCDB web interface. The list of the sub-detectors so far present is shown along with the Integration, which will contain the sub-detector interconnecting components.

The number of displayed lines can be changed via the “Option” link in the top-right corner of the panel. In addition useful helping messages are displayed when the mouse pointer is put on different sensitive areas.

Figure 8. Once the detector is selected from the central DCDB web page, then details about detector’s components and hierarchy can be extracted. Some helping dialog boxes also appear.

A useful feature in the DCDB is the histogram presenter. For any process or sub-process that can be selected via the monitor icon (see fig.8), it is possible to histogram the average pedestal value for the overall number of the FEE cards in the DCDB. An elementary analysis can be also carried out applying cuts on the histogram settings interface. Fig. 9 shows two FEE pedestal distributions without and with cuts respectively with min= 0 mV and max = 40 mV. Unfortunately, once the cuts are applied, the list of the selected cards in the distribution is nowhere available. It would be worthwhile to let the user to save the list in a text file.

Figure 9 For the overall HMPID FEE cards in the DCDB, different histograms of the average pedestal values, with different distribution cuts applied, can be produced. This elementary analysis is useful for the card selection. Unfortunately the saving of the card list in the histogram is not yet provided.

5. CONCLUSIONS

In order to test the features of the ALICE DCDB a test bench for the HMPID FEE cards have been setup. About 600 cards out of 3500 have been already tested. The relevant test results have been automatically downloaded in the DCDB via a LabView application.

The test bench is based on a LeCroy digital oscilloscope (LC564A) controlled via the LabVIEW application (using the GPIB port) and developed ad hoc by the DCDB Warsaw group. In order to define the database fields and their hierarchy we have used the user interface Dictionary Wizard. This software tool let the user to define the field types (components, process, sub-process..) and the related detector composition tree (Compositions). The defined fields contain all the relevant information about the detector components and assembling sequences. Since the same component may belong to different hierarchies, it should be clarified if the component addition or removal (design changing) has to be notified to all the concerned hierarchies or the changing propagates automatically. The central DCDB web page has been presented along with the list of the sub-detectors already defined. Among them the Integration is also reported. It will contain all the components not belonging to a specific sub-detector but requested for the sub-detector integration in ALICE. The histogram presenter of some HMPID process contents (specific test results as the pedestal average for the overall number of cards in the DCDB) has proven to be helpful in the card selection. However, once some cuts are applied on the distribution, it would be worthwhile to save the list of the selected FEE cards in a text file.

6. Appendix A

An estimate of the upper limit of the gain spread between the 48 channels of the three GASSIPLEX chips housed on the FEE card can be done using the test results reported in fig. 1 and 2. Comparing the pedestal standard deviation σped of 10.90 mV (which include the channel electronic noise) with the σsignal of 17.10 mV when the input signal is injected, then the contribution of the gain spread, including the contribution of pulse generator fluctuation, can be evaluated. In fact the σ increase is due to the folding of the capacitors value spread σcapac , which results in a different fraction of the test signal injected to each channel and the test signal amplitude fluctuation. Assuming :

2 2 2 22

σsignal = σped + σcapac + σ_∆gain + σgene (1)

σcapac = ∆C/(sqrt(12)*C)*<V_ampl >= 0.25/(sqrt(12)*5.6)*(567.70-50.30)=6.66 mV; (V=Q/C) (2)

<V_amp >=<V_sign>-<V_ped> =<V_sign-V_ped> (3)

it results

Sqrt (σ _∆gain ²+ σgene ²) = 11.36 mV. (4)

Then the percentage ∆_Gain, including the test signal amplitude fluctuation, is

Sqrt (σ _∆gain ²+ σgene ²)/<V_amp >*100 = 11.36/(567.70-50.30)*100= 2.2 % , (5)

which already is in agreement with GASSIPLEX technical specification.