Ciobanu, M.

Deppe, H.

Deppner, I.

Flemming, H.

Frühauf, Jochen

Herrmann, N.

Kis, M.

Koch, K.

Linev, S.

Loizeau, P.-A.

Manz, S.

Simon, C.

Xiang, C.

GSI Repository

Status of the CBM TOF free streaming electronics chain∗P.-A. Loizeau1, N. Herrmann1, I. Deppner1, C. Simon1, C. Xiang1,2, M. Ciobanu3, H. Deppe3, H.Flemming3, J. Fru¨hauf3, M. Kisˇ3, K. Koch3, S. Linev3, S. Manz4, and the CBM ToF working group1Physikalisches Institut, Universita¨t Heidelberg, Germany; 2Institute of Particle Physics, Central China NormalUniversity, China; 3GSI, Darmstadt, Germany; 4IRI Goethe Universita¨t, Frankfurt, GermanyThe CBM experiment will have a data acquisition sys-tem operating in free-streaming mode for most of its de-tectors. In the case of the CBM Time-of-Flight (ToF) wallelectronics chain, this new readout mode applies first to theTime to Digital Converter (TDC) and then to one or moreFPGA based boards acting as Readout Controller (ROC)and Pre-Processor [1], until the input of the computer farm.A first prototype of this readout chain consisting of thePADI3 and GET4 prototype ASICS and of the Syscorev2 ROC was assembled and tested in beam with ResistivePlate Chamber (RPC) prototypes[2]. Results of these testhelped for the development of the GET4 v1.0 chip [3] andnew versions of the PCB boards [4].Figure 1: Sketch of the setup used to take pulser data withGET4 and VFTX in parallel.These new developments were tested in beam with heavyions at GSI in November 2012 and later in the laboratorywith pulser signals. During the beam test, an RPC detec-tor was equipped with PADI6 discriminators and two Plas-tic scintillators readout by Photo-multipliers (PMT) wereequipped with PADI7 discriminators. The signals fromthe PADI boards were then splitted. On one side theywere readout in a MBS/VME based triggered system usingVFTX boards [5] as digitizer. On the other side the GET4v1.0 based free-streaming system was used. Additionaly, asignal from the trigger board of the VME system is insertedin the data stream of the free-streaming system. This pro-vides synchronization points between both systems. Thisalso allows a comparison in the free streaming part betweenan event reconstruction based on using data themselves todetect events and a “triggered-like“ event reconstruction.The pulser test is performed by replacing the 4 PMT sig-nals with a single analog splitted pulser signal. A sketch ofthis setup is shown in figure 1.The analysis software composed of an unpacker based∗Work supported by EU/FP7 I3 Hadron Physik 3 and BMBF06HD7141Ion the GO4 framework and ROOT macros is now the samefor the triggered and free streaming systems. A class forthe VFTX unpacking and calibration and a class for theGET4 v1.0 unpacking and event building are feeding thesame classes describing the detectors hits and clusters. Thedata taken in parallel can also be merged in a single outputevent using the event index sent from the triggered systemto the free-streaming system. This allows direct compari-son of the results, in particular time difference distibutions,obtained with the two systems.VFTX)03 - T00T( - GET4)03 - T00T(-1500 -1000 -500 0 500 1000 1500110210310410510 Entries  175594Mean    837.4RMS     39.12Constant  1.029e+05Mean      837.8Sigma     33.97GET4 - VFTX: Pulser signals 0 & 3 time difference, no correctionFigure 2: Example of a VFTX to GET4 comparison withpulser signals.In the pulser test, the time differences between each pairof signals in each system are fitted with gaussian distribu-tions. The difference between the time differences obtainedin each system is also computed and fitted with a gaus-sian. Figure 2 shows an example of timing performancescomparison between VFTX and GET4 based systems forthe pulser test in the laboratory. Table 1 presents the meansigma of the 6 possible signal combinations for each TDCand for their comparison.Table 1: Mean sigma of the Gaus fit for each distibution inthe pulser test for a 20mV pulse and a 150mV threshold.σ[ps]PADI7 + VFTX 17.5PADI7 + GET4 27.5GET4 - VFTX 34.5References[1] C. Xiang et al., “The online data pre-processing for CBM-TOF”, this report[2] P.-A. Loizeau et al., “CBM Progress report 2011”, Darmstadt2012, p.59[3] H. Flemming et al., “GET4 1.0”, this report[4] J. Fru¨hauf et al., “Hardware Development for CBM ToF”, thisreport[5] J. Fru¨hauf et al., “VFTX (VME-FPGA-TDC 10ps)”, this re-portGSI SCIENTIFIC REPORT 2012 PHN-SIS18-ACC-37293

Status of the CBM TOF free streaming electronics chain

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Status of the CBM TOF free streaming electronics chain

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