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Explore the advanced technologies and functional goals of the Prototype HFT system developed at STAR LG BNL DAC in March 2006. The research delves into the mechanical, electronic, and readout aspects of the innovative detector system.
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Research and Development for the HFT at STAR Leo Greiner BNL DAC 03/15/2006
STAR HFT • Two layers • 1.5 cm radius • 4.5 cm radius • 24 ladders • 2 cm X 20 cm each • ~ 100 Mega Pixels Purpose: Greatly improve charm hadron capability in STAR LG - BNL DAC - March 2006
R&D for the HFT • The mechanical aspects of this detector require significant R&D. This is also true for the electronics and readout. • Phased approach => Development of mechanical structures and first generation prototype detectors and readout in R&D phase. LG - BNL DAC - March 2006
Prototype HFT Readout Functional Goals • Digitize every 20 ns. • Triggered detector system fitting into existing STAR infrastructure. • Deliver full frame events to STAR DAQ for event building at approximately the same rate as the TPC. • Reduce the total data rate of the detector to a manageable level (< TPC rate) • Reliable, robust, cost effective, etc. LG - BNL DAC - March 2006
MimoSTAR Detector Pixel Structure • Serial raster readout • 640 pixels in a row • 320 column / sector • 2 sectors / detector • 4 ms readout time (50 MHz pixel read clock) APS detectors in a wafer LG - BNL DAC - March 2006
Prototype HFT Ladder • 20 I => V converters / drivers per ladder • Additional clock, control and JTAG connections. Power and ground • Analog signals and clock/control is transferred to the motherboard via fine twisted pair cable. • All ladders are the same LG - BNL DAC - March 2006
HFT Prototype System Functional Block Diagram The readout system is a large parallel system. The block diagram shown above is for one ladder of a 24 ladder system. LG - BNL DAC - March 2006
ADC and CDS Block Diagram • Synchronous Correlated Double Sampling and hot pixel removal. • 8 bit data after CDS. • SRAM contains a circular buffer that is an updating raster scan of 1 frame of sector readout. • Perform read – subtract – write on each clock tick. LG - BNL DAC - March 2006
(1 of 20 per ladder) To Event FIFO 320 pixels deep shift register LG - BNL DAC - March 2006
SECTOR EVENT FIFO • Each Trigger enables an empty Event FIFO for 1 frame ( 204,800 clocks) with an offset to the enable that aligns the event start time with the location of the first pixel in the event. • Each event FIFO is a separate trigger event stream and can be enabled independently. This allows events to be triggered at ~1 ms intervals with our 4 ms latency. • Each sector event FIFO is emptied by the SIU at the end of it’s active frame. LG - BNL DAC - March 2006
Implementation Diagram x5 DAQ LG - BNL DAC - March 2006
Data Rates • 100 hits/cm2 Inner Layer, 20 hits/cm2 Outer Layer (L = 1027) • Average event size = 90 KB • Event size = 90 MB/sec at 1KHz • 24 fibers • 12 RORC (4 readout PCs) LG - BNL DAC - March 2006
Ultimate HFT Detector Readout • Same physical size detector (640 x 640 pixels). • Ultimate Detectors will have on-chip CDS and remotely configurable discriminators (2 bits / pixel) • Integration (frame active) time is 200 microseconds but the readout time is 1 ms. • 4 LVDS readout lines / detector LG - BNL DAC - March 2006
Ultimate HFT Detector Readout LG - BNL DAC - March 2006
HFT Prototype Testing • Ladders – mechanical properties of prototypes and STAR environment. • Readout cable. • Preliminary air cooling tests. • Preliminary electronics developments. LG - BNL DAC - March 2006
Prototype Ladder 2 candidates Not to scale Top layer = 50 µm CFC Middle layer = 3.2 mm RVC Bottom layer = 50 µm CFC Outer shell = 100 µm CFC Fill = RVC APS (50µm) X0 = 0.05 % (thinning to 50µm is a standard industrial process) Cable X0 = 0.09 % Carrier X0 = 0.11 % Ladder Total (with adhesive) X0 = 0.282 % LG - BNL DAC - March 2006
Prototype Carrier Plot shows fundamental resonance frequency measured with a capacitance probe. Measured = 139 Hz Calculated = 135 Hz LG - BNL DAC - March 2006
Thermal Visual Images Airflow = 0 Heaters = off Airflow = 0.8 m/s Heaters = on ~27° ~20° ~25° Si temperature rise ~5-7° above ambient No hot spots, good uniformity in temperature. Emissivity is OK Upper test piece is 2 cm x 2 cm x 50 µm thick Si glued to Pt heater serpentine strip at 100mW/cm2 Lower test piece is 2 cm x 2 cm x 50 µm thick Si with Resistor heating at 164 mW along the upper edge and 90 mW distributed over the rest of the piece More information at http://www.lbnl.leog.org/ir_prelim_writeup.htm LG - BNL DAC - March 2006
Vibration from Air Cooling and the STAR Environment Airflow at 10 deg. onto prototype carrier measured at unsupported end gives measured location distribution with SD ~ 1.6 µm at 1.0 m/s of airflow Sensitive accelerometer on FTPC support shows ~ 10 µm displacements at ~1 Hz on STAR detector. LG - BNL DAC - March 2006
Prototype Cable • ~ 100 traces (2 LVDS pairs / sensor, clk, power, gnd, cntl ) • 4 layer design, 25 µm kapton, 20 µm Al conductor • Impedance controlled signal / clock pairs with power and ground geometrically arranged as shielding. Prototype Cu conductor cable X0 =0.090 % (for Al conductors) LG - BNL DAC - March 2006
Prototype Readout Electronics FPGA • Construction – bakelite carrier, cable, 1 x 50 µm MIMOSA5 detector, 1 detector (all 4 sectors) instrumented with amplifiers and differential drivers. • Motherboard and daughter card. Daughter card has ADCs, FPGA, fast SRAM. Provides CDS and memory interface. Development platform for cluster finding algorithms ADC SRAM MIMOSTAR5 LG - BNL DAC - March 2006
Summary • Prototype RDO design gives 1 KHz event rate despite a 4 ms detector latency by the use of multiple parallel buffering of events. • Design fits seamlessly into the existing STAR DAQ and Trigger infrastructure. Data from the HFT will be built into unified STAR events. • Reconfigurable FGPA based cluster finding and readout logic. • Cooling, vibration and radiation length challenges appear to be manageable. • We are starting to implement the required functionality into our prototype readout electronics. LG - BNL DAC - March 2006