Electronics

This document describes the general electronics layout and trigger philosophy for the HKS-HES spectrometer system. (For the last version of the HKS (E01-011) document see here)

Introduction

The HKS – ENGE Hypernuclear Spectrometer System consists of one hadron spectrometer for the detection of kaons (HKS) and one electron spectrometer (ENGE). The associated focal plane instru- mentation is very similar to the one that has been employed in E89-009 (HNSS). During HNSS running the electron arm (ENGE) rate was so high that each kaon event was associated with up to 8 electron events (within a reasonable coincidence time window). Therefore, a coincidence trigger was not feasi- ble and the data acquisition (DAQ) has been triggered by the kaon arm alone. The HKS-ENGE system, however, will operate the ENGE spectrometer tilted out-of-plane with respect to the splitter magnet. This will largely reduce the background rate associated with bremsstrahlung and Moeller electrons. The total electron rate should be no larger than 5 MHz. The hadron arm rate is assumed to be no more than 1.5 MHz (1 MHz π⁺, 500 Hz K⁺, and 0.5 MHz proton). This will allow to run the DAQ with a electron-hadron coincidence trigger. The total trigger rate should be kept below 1 kHz. Therefore, particle identification (PID) on the trigger level has to reduce the pion and proton rates to 1 × 10⁻⁴ and 5 × 10⁻⁴, respectively. To reduce the likelihood of accidental kaon vetoes due to multiple tracks, the hadron trigger will be segmented. <math>1\times10^{-4}</math>

General Strategy

High Voltage to all detectors is supplied from the CAEN crates on the second floor of the counting house. These crates initially have been installed to supply the G0 detector and now are a general purpose HV facility. Bundled cables, each consisting of 16 HV lines, run from the second floor to a patch panel on the left side in Hall C. The lines terminate in 16-fold connectors, used by G0, and in addition in individual SHV jacks. The G0 connectors will be unplugged and HKS will utilize the SHV jacks. From there RG59 cables will run to the two detector huts. HV settings will be controlled with the EPICS slow control system from the Hall C counting room.

TDCs

All wire chambers will use LeCroy LRS1877 multihit TDCs, 96 channels per module. All the LRS1877 TDCs will be housed in Fastbus crates in their respective electronics bunkers. The HKS and HES hodoscopes will use F1 TDCs in high resolution mode, 32 channels per module. All F1 TDCs will be housed in Fastbus crates in the Hall C counting room.

Delay lines

All ADC signals and the TDC stop signals for the HKS hodoscopes need to be delayed until after a valid trigger is formed. For this, as much as possible, the existing HMS/SOS delay lines will be employed. These lines are approximately 400 ns long.

Electron Arm (HES)

The instrumentation for the electron arm consists of a honeycomb drift and a second drift chamber, either the spare HKS or one of the HMS chambers, and a scintillator array. The scintillator array has two planes with 29 segments each and in the back one additional scintillator covering the entire focal plane for cross calibration of the two front planes. The scintillators provide the electron trigger and the start time for the drift chamber. Due to the high anticipated electron rate a segmented trigger scheme is employed.

Kaon Arm (HKS)

The instrumentation for the hadron arm consists of two drift chambers for tracking; three planes of scintillators for trigger and time-of-flight; aerogel, water, and Lucite Cerenkov detectors for particle identification. For high particle rates, the trigger can be segmented in up to 6 groups. This prevents scintillator triggers from one section of the focal plane from being suppressed by PID signals from a different section.

ENGE Spectrometer

ENGE Scintillators

There are two main scintillator planes, E1X, and E2X. Each consists of 29 vertical (x) segments. In addition, there is one long horizontal (y) bar for cross calibration, E2Y. Cables should be labeled E1X1T through E2X29B, with the E1X being the upstream plane, counters E1X1 & E2X1 located on the low momentum side of the spectrometer (negative X in spectrometer coordinates).

The Hamamatsu H6612 assembly has two short, approx. 30 cm long cables for signal and HV attached directly to the assembly. The signal cable ends in a Lemo plug, the HV cable in a SHV connector (Need to identify whether plug or jack. In case of plug need adapter or jack on cable.). The applied potential is roughly -1450 V.

To provide for adequate strain relief, it is suggested to mount two patch panels right above and below the detector (or maybe one behind). From this patch panel, 30ft RG174 (Lemo/Lemo) carry the signals from the detector level to the ground level of the hut. There the signals are split by UVA 122B signal splitters or a dedicated splitter (Lemo in/Lemo & BNC out)} for TDC/Trigger and ADC processing:

ADC

If UVA splitter, then short 16 pair flat coaxial cables connect to a JLab Flat---BNC panel. From this panel 125ft RG58 connect to the patch panel above the truck ramp. In the counting house RG58 (BNC-BNC) connect to a JLab BNC-Flat panel. From there flat coaxial cables (50 $\Omega$) connect to the existing 400 ns delay lines. These delay lines are RG58 cables connected at in- and output to JLab Flat-BNC panels.(Still need to verify the exact delay.) After the delay, 25 ft 16 pair flat coaxial cables connect directly to the LRS1881M ADCs.

TDC/Trigger

The second output from the splitter connects with 4 ns RG174 (Lemo---Lemo) to Phillips PS707 discriminators. This discriminator is a custom designed module that has one NIM and one ECL output per channel. From the ECL output, 17 pair twisted pair cables are chained to SIS3801 scalers and JLab F1 TDCs. The terminators in the SIS3801 should be removed. Optional, the scalers could also be located in the counting house and count the ``up&down coincidences. In any case, it should be verified that chaining the scalers to either the F1 TDCs or the TU FPGA does not negatively effect the performance of the TDCs or FPGA. The second discriminator output connects via RG174 (Lemo---Lemo) to Phillips PS758 logic modules that form the logic .AND. of the top and bottom tubes. From here on the signal path to the counting house is identical to the analog signals, except that the 75 ft RG58 have Lemo connectors on the hut end and BNC on the patch end. From the counting house patch, 25 ft RG174 (BNC---Lemo) carry the timing signals across the room to Phillips PS726 NIM---ECL converters in the 3rd-arm racks. Two 3 ft 17 pair twisted pair connect to the TU FPGA logic module. The FPGA forms coincidences between the front and back plane in up to a maximum of 10 groups (limited by the 10 NIM outputs of the FPGA module.) Alternatively, more sophisticated grouping could be achieved within the FPGA and only one trigger signal being extracted for trigger purposes. In contrast to the HKS detectors, grouping in the ENGE hodoscopes serves only the purpose of reducing accidental coincidences between the front and back plane.) Up to 32 signals can be extracted from the ECL outputs and recorded by scalers and low resolution TDCs for efficiency studies.

Item	Model	Channel IN	Channel OUT	Count	Location
PMT	H6612		1	118	HES hut
Patch Lemo/Lemo	???	118	118		HES hut
Discriminator	PS707	16	2 x 16	8	HES hut
Splitter	UVA 122B	16	16 Lemo/16Flat	2	HES hut
Flat to BNC	JLab Panel	4 x 16	4 x 16	2	HES hut
Discriminator	LC4413	16	2 x 16	6	CH
HV Cable 75 ft	RG59 SHV/SHV			88	Hall C
Cable 30 ft	RG174			118	HES hut
Cable 4ns	RG174			118	HES hut
Cable 2 ft	16 50Ohm flat	16	16	8	HES hut
Cable 125 ft	RG58 BNC/BNC			118	Hall C
Cable 125 ft	RG58 Lemo/BNC			118	Hall C
Cable 15 ft	RG58 BNC/Lemo			118	CH
Cable 3.6 ns	RG58			236	CH
Cable xx ft	16flat 50 Ohm			8	CH
Cable 25 ft	16flat 50 Ohm			8	CH
Delay 400 ns	JLab
TDC	F1 High Res.	32		3	CH
Scaler	SIS3801	32		3.5	CH
ADC	LRS 1881M	64		2.5	CH
FPGA Logic	Tohoku TUL	64	10 NIM+?ECL	2	CH

Honeycomb Drift Chamber

The electron arm has one honeycomb drift chamber, HC1 with approx. 1200 channels. HV is supplied via 5 RG59 cables at a potential of roughly -2200V. The anode wires are read out by 70 Nanometric amplifier discriminator cards (see Section~\ref{sec:nanometric}). Each card reads 16 channels. The power consumption per card is 5.4 W (+5 V, 0.4 A, and -5 V, 0.68 A). The low power supply (Acopian???) needs to provide at least 28 A at +5 V and 48 A at -5 V. The discriminator threshold is set by an external voltage provided by a BK Precision 1660 power supply, located in rack CH03B10 in the electronics area of the counting house. The optimal threshold at the operating point of the chambers is $x.yy$V. This is set with a dial on the front of the device. Each discriminator output is connected by 34-pin (17 pair) twisted-pair cable to a (LRS 1877 96 channel pipeline FASTBUS TDC (15 modules)) JLab F1 TDC with 64 channels per module in low resolution mode (18 modules). The TDCs trigger signal is distributed via a fan-out and NIM-ECL converters.

HKS Spectrometer

High Voltage

All high voltage to the HKS detectors will be supplied from the G0 HV crates on the 2nd floor of the counting house. From the counting house bundles of 16 cables each lead to the G0 HV patch panel in Hall C. From there, ~140ft RG59 cables, SHV connectors on both sides lead to the HKS bunker. The following table gives the channel and module count:

Detector	Channels	A503 -3 kV, 3 mA	A503 +3 kV, 3 mA	A505 -3 kV, 200 uA	SY403 HV crate
DC 1&2	4			1/4	1/4
HHODO	88	6			6/4
HAC	42		3		3/4
HWC	48	3			3/4
HLC	26	2			2/4
Total	208	11	3	1/4	4

Media:HV patch assignment.pdf

Scintillators

There are three scintillator planes, H1X, H1Y, and H2X. H1X consists of 17 vertical (x) segments, H1Y of 9 horizontal (y) segments, and H2X of 18 vertical (x) segments, for a total of 44 detector or 88 channels. The electronics layout is shown in the figure below.

The Hamamatsu H1949-50 2-inch photomultiplier tube assemblies (R1828-01:Media:R1828-01.pdf) have two anode outputs. One output is send directly to the counting house where, after appropriate delay, it is recorded by an ADC. Before being send to the counting house, the second output is discriminated in the detector hut. For this Phillips PS706 (Media:PS706.pdf) or PS707 (Media:PS707.pdf) are employed, which both provide Lemo (NIM) connectors on the output. In the counting house, the timing signals are discriminated again to compensate for cable losses and dispersion. At this point, no Lemo outputs are necessary. Thus, LeCroy 4413 (Media:LC4413.pdf) with 2 x 16 ECL outputs can be used. From the 2nd discriminator, ECL signals are distributed to F1 TDCs (high resolution mode; 32 channels/module), scalers (SIS3801), and TUL logic modules for mean time and trigger processing.

For the horizontal layers, H1Y, a simple logic .OR. is formed. The vertical layers, H1X & H2X are assigned into 6 groups (for H2X those are overlapping). On its NIM outputs, the 1st TUL will provide a H1Y OR, H1X OR and 6 grouped signals H1X I - H1X VI. The 2nd TUL provides the H2X OR and 6 grouped signals H2X I - H2X VI. Thus, the total number of NIM outputs from the two TUL modules is 15. One 16 channel twisted pair cable, split on one end, will collect these for recording in scalers and low resolution TDCc for rate and trigger efficiency studies.

Item	Model	Channel IN	Channel OUT	Count	Location
PMT	H1949		2	88	HKS hut
Discriminator	PS707	16	2 x 16	6	HKS hut
Discriminator	LC4413	16	2 x 16	6	CH
HV Cable xx ft	RG59 SHV/SHV			88	Hall C
Cable 150 ft	RG58 BNC/BNC			88	Hall C
Cable 150 ft	RG58 Lemo/BNC			88	Hall C
Cable 30 ft	RG58 or RG174 BNC/Lemo			88	Hall C
TDC	F1 High Res.	32		3	CH
Scaler	SIS3801	32		3.5	CH
ADC	LRS 1881M	64		2.5	CH
FPGA Logic	Tohoku TUL	64	10 NIM+?ECL	2	CH

Cable Issues

None of the three groups, H1X, H1Y, H2X has channel counts modulo 16 or 8. Thus, they cannot easily be mapped on the 16-channel twisted pair cables without increasing the number of discriminators, scalers, and TDCs. The scheme presented above employs in the Counting House 6 16-channel discriminators. This requires the careful preparation of one cable that carries 4 signals each from H1X and H2X to two different TUL modules. This could be avoided at the additional expense of one more discriminator and 1/2 each of scaler and TDC.

Aerogel Cherenkov

There are three layers of aerogel detectors, HA1, HA2, and HA3. Each layer has 7 segments. Each segment has two tubes; top and bottom. They are named HA1T1, HA1B1, ... , HA3T7, HA3B7. Counters #1 are at negative spectrometer x and counters #25 are at positive spectrometer x. All aerogel electronics and HV supplies are upstairs in the counting house.

Aerogel PMTs

The aerogel detectors use two different types of photomultiplier tubes, Hamamatsu R1250 and Photonis XP4572B/D1. Both types are operated in a kathode ground scheme (positive HV to anode). The Hamamatsu R1250 use voltage dividers built at FIU. The Photonis XP4572B/D1 use the Photonis VD305 voltage divider with an additional amplifier built at JLab added diretly into the divider housing. The amplifier does not require a low voltage supply; it gets its power from the last stage of the voltage divider. The PMT anode signals are directly connected with 125 ft RG58 (BNC-BNC) to the Hall C patch panel. In the counting house, the signal first runs through a splitter (or linear fan in fan out). One branch gets delayed by ≈ 400 ns and goes to the ADCs. The second branch goes to discriminators (either PS707 or PS7106)in the 3rd arm rack. One Tohoku University FPGA module forms the desired logic (.AND.and segmentation). The discriminated signals before the logic as well as up to 32 signals after the logic are send to scalers and low resolution TDCs for trigger studies.

Water Cerenkov

There are two layers of water Cerenkov detectors, HW1, HW2. Each layer has 12 segments. Each segment has two tubes; top and bottom. They are named HW1T1, HW1B1, ... , HW2T12, HW2B12. Counters#1 are at negative spectrometer x and counters #12 are at positive spectrometer x. All water Cerenkov electronics and HV supplies are upstairs in the counting house. The electronics layout is shown in Fig.5. It is essentially the same as for the Aerogel Cerenkov.

Lucite Cerenkov

There is one layer of Lucite Cerenkov detectors, consisting of 13 bars of acrylic plastic. At both ends the light will be collected by 3-inch PMTs.Before being sent up to the counting house, the PMT signals will be amplified by Phillips Scientific NIM MODEL 778 16 Channel Variable Gain Amplifier (Media:PS778.pdf). The PS778 has two outputs. One will be sent straight to the counting house; the other will be summed with the corresponding 2nd tube on the bar and sent to the CH for PID trigger.

• In the CH all 39 signals will be split.
• The ribbon outputs will be sent through the usual ADC delay lines and to ADCs.
• The 13 summed signals will be discriminated (high threshold between protons and kaons), grouped in a TUL module and send to the PID trigger.
• The 26 direct PMT signals with be discriminated (low threshold), grouped, and used to form a hodoscope charged particle trigger.

Drift Chambers

The kaon arm has two drift chambers, each with roughly 650 channels. They are read out by a total of 80 Nanometric amplifier discriminator cards (see Section ??). Each card reads 16 channels. The power consumption per card is 5.4 W (+5 V, 0.4 A, and -5 V, 0.68 A). The low power supply (Acopian???) needs to provide at least 32 A at +5 V and 55 A at -5 V. The discriminator threshold is set by an external voltage provided by a BK Precision 1660 power supply, located in rack CH03B10 in the electronics area of the counting house. The optimal threshold at the operating point of the chambers is x.yyV. This is set with a dial on the front of the device.

Drift Chamber Readout

Each anode wire has its own electronic readout through Nanometric N277 preamplifier/discriminator cards (or LeCroy Corporation LRS 2735DC cards which are interchangeable with the Nanometrics cards). Each of these Drift Chamber cards has 16 inputs which accept negative signals from the anodes (sense wires), amplify and then digitize the signals according to whether a user-specified threshold level is crossed. This threshold level is set using a low voltage (0 to 10 volts) dc power supply. A multi wire cable connects this threshold power supply to the Drift Chamber cards. Each of the Nanometrics or LRS cards requires approximately five volts (bipolar) and approximately 1/2 A. This power is supplied by Acopian supplies. Each discriminator output is connected by 34-pin (17 pair) twisted-pair cable to LeCroy Model 1877 96-channel FastBus TDCs.Media:LRS1877manual.pdf

Module	Number
LRS1877	14
Acopian +5V	1
Acopian -5V	2

Trigger

Hadron Particle Identification Trigger

The minimum requirement for a hadron trigger is a valid scintillator trigger. Only pions produce light in the aerogel ˇCerenkov. The threshold is set to ≈ 1 p.e. for an individual tube. Kaons and protons will both create light in the water ˇCerenkov. The lightoutput for kaons, however, is higher than that for protons. The discriminator thresholds are set between the kaon and proton distributions. Four signatures are possible:

Table goes here

The following trigger strategies could be employed:

• Build the kaon trigger. Prescale the scintillator trigger.
• Build all four possible triggers.
• Build the pion, kaon, and proton trigger with the “undefined” included in either the proton or

pion trigger.

Fig.7 shows the particle ID triggers. Prescaling can be achieved by:

• Prescaling circuits: “the signal bites it’s tail.” The prescaling factor is not well defined, i.e. it is rate dependent. The exact factor can be determined from a scaler analysis.
• Prescale at the trigger supervisor.

Coincidence Trigger

The following table lists the electronics required to form the pretriggers for the twospectrometers. At present, it includes the logic required to make the Hadron PID triggers (Fig. 7), but not the combining and prescaling of these 3 particle types to make a single Hadron pre-trigger.