R  I  C  H     T I P S   &   H I N T S



 1) Monitoring LEDs:
	 There are 4 chains of blue LEDs for monitoring mounted
	on the top and the bottom of mirrors supporting frame.
	Each LED is mounted on its own driver card. There is a
	tech-note about this driver card H-754 (file LED.ps in
	~kozh/RICH2001). Each chain requires +12V power supply 
	and POSITIVE trigger pulse  (+2V - +5V, 50-100 ns). The
	last driver card in each chain has terminator to 50 Ohm.
	 Connectors for these LED chains are on RICH downstream 
        flange. They are BNC type. Outlook is shown here (if looking
        on connectors):
 
                        EMPTY    EMPTY    EMPTY
                12VA    12VB     TRIGA    TRIGB    EMPTY
                T1U     EMPTY    T2U      EMPTY    EMPTY
                12VC    12VD     TRIGC    TRIGD    T3U
                        T1L      T2L      T3L

       12VA-D       - +12V power for LED drivers,
       TRIGA-D      - trigger pulses,
       T1U,T2U,T3U  - upper thermocouple inside vessel,
       T1L,T2L,T3L  - lower thermocouple inside vessel
                      (each thermocouple has 3 isolated wires).


 2) HV system:  
	 HV system consists of 6 Russian made HVPS (2 kV, 200 mA, 
	220V AC, powered here in Fermilab from 208V 2-phase AC),
	distribution box based on zener diodes and HV interlock
	system. There are 8 HVPS available in total (probably they
	still are Moscow State University property). 
	 Zener box has 6 HV inputs (SHV connectors on back side) and 
	outputs for each column (short cables with SHV connectors 
	on front side). All PMTs in one column have the same HV. 
	Column number is marked on the outgoing from zener box cable.
	Each zener chain has its own load to provide minimum current 
	through it. There are two cooling fans (120V AC power) which
	have to be on during zener box operation to avoid overheating
	of zeners and loads. Power for them is provided by standard
	120V outlet plug with cable.   
	Voltages on inputs are the following:
	#1 (uppermost)	- 1380V  (Russian FEU-60),
	#2              - 1270V  (Hamamatsu R-760),
	#3		- 1580V  (Russian FEU-60),
	#4              - 1280V  (Hamamatsu R-760),
	#5		- 1940V	 (Russian FEU-60),
	#6		- 1680V  (Russian FEU-60).
	 There are control outputs from control dividers for each
	zener in the chains and loads located on the front panel 
	of the box: 3 control groups with multi-pole switch and 3
	BNC connectors in each group. Each load has also separate
	control output in the bottom of front panel. Normally You
	have just to check load voltages. If load voltage reading
	is OK and input HV reading is OK, that means all zeners in
	this chain are OK. You could also find a table of all 
	control voltages in RICH log book. Control address here is
	1-st digit - control group, 2-nd digit - BNC connector in
	that group, 3-rd number (dash separated) - switch position.
	 HV is entering PMT box via feed-through panel near zener box.
	A map of this panel is also somewhere in log book. In general
	just looking on number on zener box cable is enough. Each 
	column consists of two half-bundles, HV wires from all PMTs in
	the same bundle are soldered to one small paddle card. Ground
	wires to another paddle card. Paddle cards are mounted on
	special isolated structure separated from each other with G10
	sheets. Two paddle cards for the same column are connected with
	short jumper wire.
	 Normally HVPS are powered through HV interlock box, which has
	two interlock inputs from interlock chain inside PMT box. Chain
	consists of 3 door switches and 3 thermo-switches hidden 
	somewhere between PMT bases. Chain need to be closed for 
	interlock to operate (You could use 50 Ohm BNC terminators for 
	that). When this chain become open, main circuit breaker on 
	the front of the box will trip. 
	 Each HV power supply also requires "HV off" input to be close
	to ground for HV output to be enabled. You could also use 50 Ohm
	BNC terminator to bypass that. But in normal operation this
	input was connected to the RICH HV overvoltage protection box
	output. This box takes control readings from each PS control
	output and compares them with preset thresholds. If reading is
	below threshold, output for this PS is close, HV is enabled. 
	Otherwise overvoltage protection trips this HVPS opening this
	circuit. To restore operation reset switch on the front of the
	overvoltage protection box need to be operated manually.


 3) PMTs and PMT bundles:        
	 Each column has two half-bundles, 16 PMTs each, tight together.
	Each bundle has its own signal paddle card with signal 
	connector (multi-pin EURO type), HV paddle card with all HV 
	wires soldered on it, and ground paddle card with all ground
	wires soldered to it. Signal cables are RG-58 or equivalent
	type from each PMT to paddle card. There are 1 kOhm SMD type 
	very small resistors soldered on signal paddle cards as signal 
	loads. It is highly recommended to check them all and replace 
	damaged ones at some point. There are for sure some of them 
	damaged now. This usually happens when PMT sparks or has 
	other HV problems. This signal paddle cards are connected to
	the backplanes of preamp crates on the top of the PMT box.
	And they are hold only by its connectors. 
	 Russian PMTs FEU-60 are soldered to the bases. They have soft
	leg wires and can not be detached from the base. Hamamatsu R-760
	have usual socket type connection to the base. Spare Russian PMTs
	which are sorted by voltage and bundle number are in separate
	envelopes with voltage, bundle (not column!) number, and 
	individual PMT numbers on each envelope. Unsorted PMTs are 
	stored in the folders by batches as they were measured last
	time. On each folder a list of PMTs in this batch is attached 
	with measured efficiency, noise, selected working voltage, etc.
	 Working voltage for Russian FEU-60 was set to the point with
	30 kHz PMT noise, and efficiency was measured at this point.
	For Hamamatsu R-760 working point was set to the middle of 
	efficiency plateau. Noise from R-760 usually is much less - 
	typically less than 1 kHz. Working voltage for them is also
	less than for Russian FEU-60. This Hamamatsu PMTs are limited
	to 1250V by HV. Russians could be run at up to 2000V.
	 Phototubes are installed each inside its own hole in
	aluminum photocathode plate. They are about 3/4 length deep in
	that plate. As a matter of holding them just a piece of
	paper masking tape was used over each PMT for Russian FEU-60, 
	and 3 narrow velcro strips attached to each Hamamatsu R-760 
	tube. That provides some friction which holds the PMT in
	its hole. But it is usually very easy to pull it out. So
	after replacing one tube it is important to check that  all 
	neighbors are fully sitting in its holes.
	 Repairing of not working PMTs most likely means just 
	replacing them by spare ones. For this just cut all wires 
	from not working one and solder to the corresponding wires 
	of spare one, then put some masking tape over it, and put it
	into the hole in the photocathode plate.
	 To protect PTP wavelength shifter coating a very tiny mylar
	O-rings are installed between quartz window in photocathode
	plate and PMT surface. It is unlikely that anything could
	happened with them, but this information is useful anyway.
	 Hamamatsu R-760 are used only in central part of the 
	detector, where Hamamatsu columns and FEU-60 columns are
	alternating. In total there are 19 Hamamatsu R-760 columns
	(32 X 19 = 608 PMTs). 


 4) Preamplifier-discriminator hybrids:
	 Signal from each PMT is connected to preamplifier-
	discriminator hybrid chip. Cards with them are located in
	custom made crates on top of the photocathode box. There is
	one card with 32 channels (hybrids) per each column. There
	are 3 crates in total, 32 slots each. Only 30 slots are
	used in each crate, 2 slots are spare (usually right and 
	leftmost slots). 
	 Each card has 2 input signal connectors (EURO type), 2 34-pin
	output connectors for standard 17 twisted pair flat cable,
	and 3-pin power connector. Hybrids require +6V and -6V. 
	Current consumption is rather big ( ~1.3 Amps per card for
	-6V, and ~0.8 Amps per card for +6V). Card power inputs are
	fused, small fuses are located just near power connector. 
	For -6V 2 Amp slow blow fuse is used, and for +6V - 1 Amp
	the same type one. Fuses are very easy to blow, for example
	if chip misalignment would occur.
	 Hybrid chips are mounted on individual sockets. There are 
	two types of them with different threshold: 2.5 mkA for 
	Russian FEU-60 and 5 mkA for Hamamatsu R-760. In output chip
	produces a 30 ns differential ECL pulse for each input 
	signal above threshold. Input signal shall be negative to
	the ground and not exceeding 0.6V in amplitude. 
	 There were several generations of those chips used mostly
	Russian made. But unfortunately Russian made chips are
	looking totally unreliable now because of very big malfunction
	rate. There are also ~500 US made hybrids, which are much
	better and reliable.
	 LV power is provided for hybrid cards via power lines on 
	crate backplanes. In terms of power slots are connected in
	groups of 8, each group has separate power entry and fuses.
	Power is connected to the crates via feed-through rods on the
	back of the crates. This area is actually pretty unaccessible
	now. To do so You'll have to remove cooling ducts completely.
	 The rack with low voltage power supplies is near the RICH 
	photocathode box. Usually six 60 Amp 6V power supplies were
	used (two PS per crate). All PSs are powered through LV
	interlock box which provides power shutoff in the case of
	chips overheating. This box was using input from temp sensors
	system. There were 3 temperature probes installed in the
	middle part of each crate. If the reading of any of those
	probes was exceeding threshold, power for the whole LV rack
	was tripped off by this interlock box.