sPHENIX discussion of electronics

[Martin Purschke <purschke AT bnl.gov>]

Dear sPHENIXionados,

I'm planning to submit the following abstract to the Nuclear Science
Symposium (end of October in Strassbourg). Please don't hold back with
suggestions, praise, or flames.

        Best,
                Martin



-- 
Martin L. Purschke, Ph.D.        ;   purschke AT bnl.gov
                                 ;   http://www.phenix.bnl.gov/~purschke
                                 ;
Brookhaven National Laboratory   ;   phone: +1-631-344-5244
Physics Department Bldg 510 C    ;   fax:   +1-631-344-3253
Upton, NY 11973-5000             ;   skype: mpurschke
-----------------------------------------------------------------------

The recently established sPHENIX Collaboration at RHIC is upgrading
the PHENIX detector in a way that will enable a comprehensive
measurement of jets in relativistic heavy ion collisions. The upgrade
will give the experiment full azimuthal coverage within a
pseudorapidity range of $-1.1 < \eta < 1.1$. In addition to measuring
heavy-ion collisions, the new apparatus will provide enhanced physics
capabilities for studying nucleon-nucleus and polarized proton
collisions, and eventually allow a detailed study of electron-nucleus
collisions at an envisioned Electron Ion Collider at Brookhaven.

The upgraded detector will be based on the former BaBar magnet and
will include tracking detectors, a new electromagnetic calorimeter,
and, for the first time at a RHIC experiment, a hadronic
calorimeter. A new technology using a Tungsten-scintillating fiber
design for the electromagnetic calorimeter is what enables the full
azimuthal coverage, as it achieves a radiation length of just about
7mm, which allows for a very compact design of the device.
 
The calorimeter signals are sampled with silicon photomultipliers and
waveform digitizing electronics. The digitized waveforms are read out
with custom PCIe boards that allow multiple streams with bandwidths of
up to 5GBit/s. The goal is to have a sustained event rate to disk of
about 15KHz. Focusing on the calorimeters, we will describe the goals
and design of the sPHENIX experiment, the design of the digitizers and
other parts of the data acquisition system, and the results we got with
current prototypes. By the time of the conference, we will have data
from a test beam at FermiLab that will test the readout under beam
conditions.

We will detail the design of the FPGA-based readout cards, and how we
implement the so-called "multi-event buffering" in the front-end,
which has traditionally enabled PHENIX to take data at rates rivaling,
or exceeding, the LHC experiments.