1. Summary of the Barcelona Meeting March 10 th and 11 st, 2009 Calorimeter Upgrade Meeting Frédéric Machefert On behalf of the Barcelona and Orsay Groups Albert Comerma, Carlos Abellan, Christophe Beigbeder, David Gascon, Eduardo Picatoste, Eugeni Graugès, Frédéric Machefert, Jacques Lefrançois, Jordi Riera, Lluis Garrido, Olivier Duarte Thursday 26 th March 2009

2. Calorimeter Upgrade Meeting2 Meeting at Barcelona ● The meeting took place at Barcelona on March 10th and 11 st 2009 – 2 sessions : ● Analog electronics ● Digital electronics ● Slides and Minutes are available from – http://indico.cern.ch/conferenceDisplay.py?confId=54924

3. Thursday 26th March 2009Calorimeter Upgrade Meeting3 Analog electronics specifications (I) ● Specifications and comments – The transverse energy range should be 0-10GeV/c on 12 bits ADC – Clipping is probably needed to have a plateau, otherwise sampling would be done on a slope of the integration curve and the measurement would be very sensitive to particle time arrival ● Gaussian shaping could also be studied – The PMT gain should be reduced by a factor 5 with respect to the curren t gain ● The electronics gain should be increased accordingly – Noise requirement corresponds to ~1ADC count or ~5fC (25/5 fC) ● A clipping at the PMT base means 25Ω in parallel to 50Ω – This resistance determines the current to voltage conversion and as it becomes small a low noise preamp is needed (<1nV/Sqrt(Hz)) – The possibility to have the clipping on the FEB after the pre-amplifier is to be looked at ● Having the amplifier on the base would induce a large intervention on the detector and has some radiation tolerance implications – The pre-amplifier should have a well controlled input impedance ● In case of clipping on the base an active termination is needed. A resistor would induce too large a noise and an active line termination circuit would accurately set the input impedance.

4. Thursday 26th March 2009Calorimeter Upgrade Meeting4 Analog electronics specifications(I) – AC coupling could be used thanks to the dynamic subtraction. With DC coupling part of the dynamic is swallowed by the pedestal. – The radiation tolerance should reach 10 or 20 krad in 5 years – In order to reduce the space used and be able to integrate the optical outputs, groups of 8 channels are desirable. – A rough (gu)estimation leads to a cost <25€ per channel

5. Thursday 26th March 2009Calorimeter Upgrade Meeting5 Switch versus Delay line solutions ● Switch induces a large pedestal. Its stability could be an issue although on the SPD this was not a problem – Switch on SPD removes ~30% of the dynamic (DC). This range should not exceed 5% on the ECAL (done with AC coupling) – Pedestal has two origins : ● Component mismatch : a constant of the system and the dominant source ● Switch charge injection and integrator – Solutions envisaged : ● AC coupling would solve the problem of the reduced dynamics – The AC coupling time constant should be more than 5  s not to be sensitive to the bunch gap ● DC coupling with pedestal compensation (DAC integrated ?) ● Gain of the two subchannels of the switch may be different – Digital correction could be necessary (how many bits ?) ● But switch advantages : – Highly integrated – Available latching time of the integrator is almost 25 ns ● This permits to have a multi-channel ADC with a single clock – The sampling plateau should be wider than with a delay line integrator

6. Thursday 26th March 2009Calorimeter Upgrade Meeting6 Comparison ASIC vs Discrete Solution ● Discrete solution should use Op. Amp. (not at transistor level) – Room and reliability ● Whatever the solution, power consumption should not be an issue ● Room is an issue (GBT+optical links) – 6U (height) x 30% of the width is allocated to the analog part – Composent could possibly be soldered on both sides

7. Thursday 26th March 2009Calorimeter Upgrade Meeting7 Two scenarios ● Clipping 1) We want to have a clipping on the base ● Need an ultra low noise system with an accurate input impedance of the pre- amplifier ● This would probably imply the design of an ASIC 2) Clipping on the base could be removed ● The noise constraint is not so strict ● The PMT base modification is minor (a line to cut on the base PCB) ● A 50 Ω resistor at the FEB input should be enough to adapt the line ● Design : – Discrete solution : the design could be done “quickly” ● Low noise pre-amp ● Delay line clipping ● Delay line integration – ASIC solution ● Delay line clipping and delay line integration ● Delay line clipping and integration by switch ● Gaussian type shaping (no clipping but tail to be looked at) and integration by switch

8. Wednesday 20th February 2008 Calorimeter : Commissioning Meeting FPGA : AX or PA3 ? (I)‏ ● Two problems have been observed with the APA FPGA – W hen two many bits flip altogether and quickly, the signals seen after the input buffers of the FPGA are corrupted. This is hardly documented by the manufacturers and the acceptable limits (number of bits flipping, average rate) depend on the implementation. – When sending several bits on the FPGA inputs, the internal sampling of the signals by a unique external clock (and in spite of the usage of a dedicated clock tree) seems to be done with phase shifted clocks among the registers. This makes « synchronized » sampling of fast signals more difficult. ● It seems that we need to perform our own tests in order to find and be persuaded of the “good” solution. Two ways of testing the FPGA have been thought of : – Having a prototype dedicated specifically to that problem, – Using the FE-prototype to test the FPGA capabilities. ● It appeared that the second way is not favoured as it would increase the complexity of the design of the FE-prototype both in term of PCB and firmware.

9. Wednesday 20th February 2008 Calorimeter : Commissioning Meeting FPGA : AX or PA3 ? (I)‏ ● H ence, we think that two prototypes have to be made. – A first prototype to study the performances of the components. – The second prototype would integrate a digital readout of the analog signals and be the FE-prototype. ● This means that the latter would be delayed in time as the first conclusions on the former need to be obtained. ● ProAsic3 seems to be easier to use (reprogrammable) and would be the baseline. Still, we may imagine that it cannot cope the signals exchanged. The AX would be the backup solution. But, we also have to prove that the AX may work. ● On the present front-end board we benefited a lot from the Silicon Explorer to debug the firmware. This does not exist on the APA. It seems that something similar exists on the ProAsic3. The following questions were raised : – Price of the system – Resources needed to make it work

10. Wednesday 20th February 2008 Calorimeter : Commissioning Meeting First Prototype (I)‏ ● T he first prototype would include – A ProAsic3 – A socket to receive an AX – The possibility to exchange data ● Between the AX and the APA ● From an FPGA to itself – A SPECS mezzanine connector – A digital readout connector : the possibility to perform a readout of the digital implementation was thought of at this level. We imagined to have a connector on our prototype and be able to connect a mezzanine having the analog part up to after the ADC (Barcelona). This would help in checking that the readout may be performed with the FPGA chosen and may help in having an early and simple readout for Barcelona. – The GBT standard is not well adapted to the FPGA outputs. We have to design a system to make the FPGA and GBT compatible. This system should be tested on this first prototype. If the FPGA-GBT link is mono-polar, a simple tension divisor was imagined but this would increase the overall consumption (back of the envelop calculation ~ 1A/80 outputs). The problem is more acute if we want to have differential outputs (and use the high speed capabilities of the GBT). NB : the FPGA bit flip problem was linked to the I/O current.

11. Wednesday 20th February 2008 Calorimeter : Commissioning Meeting First Prototype (I) – Second Prototype – W e probably have to plan an interface with the analog mezzanine if this capability is confirmed : clock, SPECS, etc... ? – Two reception areas for two delay chips. Only one would be connected at a time but we would have the possibility to solder either a Delay25 (CERN) or a LAL delay chip. – This board would be used « on the table », powered with test bench power supplies. – The difficulties experienced with the i 2 c and FPGAs lead to the test of the transactions with the FPGA on the prototype already. – The possibility to use the first prototype for irradiation tests was mentioned. But the conditions and purpose of those tests have to be defined precisely. ● The second Prototype would use : – The components tested with the first one – No component testing with this board – The futur trigger implementation was supposed to be identical to the present one. This has to be confirmed but seemed clear to us. The question of integrating it to the second prototype was raised.

12. Thursday 26th March 2009Calorimeter Upgrade Meeting12 First Prototype ● Schematic of the first prototype

13. Thursday 26th March 2009Calorimeter Upgrade Meeting13 Tasks and Schedule ● We plan to have a new meeting on April 8 th and 9 th at Orsay – Some questions should be answered ● Noise issue should be more understood in case of clipping ● What is the effect of the cables ● Gaussian shaping will be looked at (no clipping but tail ?) ● Pedestal in a switch system – SPD experience – Pedestal after AC coupling – Offset trimming to recover the dynamics – First study of a discrete solution – Usage of the latest software versions to compile the present firmware – Usage of the present firmware on the possible targets (AX, ProAsic3) – Rough idea of the needed resources (I/O, PLL, RAM, banks,...) ● Schematics of the first PCB prototype by June – PCB by the end of the Summer ?