404 10th INTERNATIONAL CONFERENCE AND SEMINAR EDM'2009, SECTION VI, JULY 1-6, ERLAGOL

Development of the New Unified InputSignals Shaper of the Primary Triggerof the KEDR Detector at VEPP-4M

Pavel V. Kas'yanenko', Student Member, IEEE, Alexey A. Talyshev'1Novosibirsk State Technical University, Novosibirsk, Russia

2BINP SB RAS, Novosibirsk, Russia

Abstract - The new unified shaper of the primary trig­ger input signals of the KEDR detector at VEPP-4Mwas developed. General structure of the primary andsecondary triggers of the KEDR detector is described.

Index Terms - Accelerator, Collider, VEPP-4M, KEDRdetector, primary trigger, signals shaper.

I. INTRODUCTION

THE VEPP-4M ACCELERATING-STORAGEcomplex is the unique Russian particle collider

in the 2-12 GeV energy range (center-of-mass refer­ence system). Moreover, owing to some characteris­tics, this complex is the unique facility on a globalscale. The VEPP-4M is designed for high-energyphysics experiments. Now, the basic instrument tostudy elementary particles and fundamental proper­ties ofmatter is the colliding beams method.

One of the main apparatus working with accele­rator is the KEDR detector - universal magneticdetector of elementary particles designed to work inenergy range from 2 to 12 GeV at the center-of-masssystem [1].

During experiments at the VEPP-4M and KEDR,masses of the J/psi, psi' andpsi(3770) mesons wasmeasured. These measurements are the world mostprecise result. At 2008 tau-lepton mass measurementexperiment was fmished with the world best accura­cy, and it have considerable impact on determinationof the Standard Model limits [2].

While detector running upgrade was found to beessential in order to extend it function abilities andto improve it technical performance.

II. PROBLEM DEFINITION

Detector consists of several subsystems, whichitself contain thousands ofmeasuring channels.

Besides of useful events detector catches largeamount of «garbage», to suppress it the primary(PT)and secondary(ST) detector triggers designed. Thesignals are provided to the input of the triggerthrough the shapers where they are treated withsome logic actions. In total we have 96 input signals

from Scintillating Counters (SC), 96 signals fromCsI calorimeter and 192 signals from Lkr calorime­ter.

The structure scheme of triggers is shown atFig. 1 [3, 4].

Input signals from one beam event arrive triggerat the time interval from 20 to 250 ns, due to differ­ent response latency of the detector subsystems.Trigger must make a decision during 450 ns. Triggerdecision time is smaller than time between beamscollisions, so that trigger have no dead time, and canprocess each beam event. Such short working timeputs strong constraints on detector subsystems usa­ble for PT. There are only three systems - scintillat­ing counters (Time ofFlight system - TOF), CsI andLKr calorimeters are signal sources for primary trig­ger.

When PT forms positive decision, the blockingsignal are issued, and secondary trigger startsprocessing. If it makes positive decision too, thendigitizing and reading out of event data begins. Thenblocking signal is turned off and system ready toprocess next event.

In order to obtain more event details, to providemore extensive trigger test and more flexible controlof shaping time of detector signals new "unifiedshaper block" was developed.

III. THEORY

To solve the problem FPGA Altera(EPIC3TI44) was used. Shaper block designed toconform CAMAC standard and has size of 3M. Ithave 48 inputs.

Top level file of the shaper project at QUARTUSfor FPGA Altera is show at Fig 2. Pll is a generatorof the working project frequences 250MHz and20MHz. They are formed from input frequency 20Mf'u, The 'Camac' module, provides interface be­tween the project and CAMAC bus.'Wait_cntl_multichannel' is the main project module,it has 48 identical channels. In each channel on inputrising new pulse formed. Length of that pulse is con­trolled by the computer (bus time[7..0]) and can be

978-1-4244-4572-1109/$25.00 © IEEE

KAS'YANENKO and TALYSHEV: DEVELOPMENT OF THE NEW UNIFIED INPUT SIGNALS SHAPER ... 405

varied up to 1024 ns with step 4 ns. Then shapedsignals gets to module 'form', which gathers them bylogical «OR», and also counts number of hittedchannels. Each channel also contains 24-bit cymo­meter. Input signals can be masked (by logical«AND») through the bas mask[], which is computercontroled too. All modules are written in AHDLlanguage

IV. EXPERIMENTAL RESULTS

The shaper block was produced and program forFPGA Altera was written. The computer program towork with and test shaper was developed. Work ofthe block, frequency metres is checked up, oscillo­grams are received. On Fig. 3 test oscillograms ofwork of the block are shown. On 10 and 30 inputs ofthe block impulses from the generator with frequen­cy of 1 730 517 Hz are submitted, on one of them isdirect, on another - through a delay line.

Input and target signals of the block have formatNIM, the current standard, logic 0 there correspondsa zero current, logic 1 - a current-16 MA whichcreates a voltage drop 0.5 V on the matched load 50Ohm (signals are transferred through a coaxial cableby wave resistance 50 Ohm).

On Fig. 4 the main window of the program isshown, allowing to set time formings and to observethe measured frequency in each channel (in drawingthe signal is submitted only on 10 and 30 channels),on Fig. 5 - the masking window, allowing to switchon and off channels in the block.

V. DISCUSSION OF RESULTS

Use of this block allows to fmd out operativelyfaulty channels (the raised or insufficient loading(frequency)) and to mask them. Allows~MrespOnSecTaHUMoHHO to adjust time forming fordifferent systems of the detector. The position in­formation on response of channels can be read to­gether with event.

VI. CONCLUSION

The block with following possibilities is made:Formation of a signal set (set from the

computer) durationThe Output OR all channels (formed and

not formed)The Counting of the worked channels or

quantity of stains, depending on a configuration.Frequency Measurement in each channelMasking of channels.

REFERENCES

[1] http://kedr.inp.nsk.su/[2] http://v4.inp.nsk.su/

[3] S.S. Petrosyan. Trigger of the detector the KEDR in aseason 2005 - 2006. (In Russian).

[4] V.1. Telnov. The trigger of the detector the KEDR (InRussian).

406 10th INTERNATIONAL CONFERENCEAND SEMINAREDM'2009, SECTIONVI, JULY 1-6, ERLAGOL

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