Glossary & Acronym List of G0 Terms which drive people crazy.
Compiled by Greg Smith: send new ones to me and I'll add 'em here.
5/14/2004
Term	Meaning (my interpretation, anyway)
120 Hz	Oversampling the data. Reading out 4* more often than the helicity is changing.
30 Hz	Approximate helicity reversal frequency.
ABU	Acceptable Beam in Use.
adiabatic damping	Property by which the transverse emittance decreases as the momentum increases. Adiabatic means no net gain or loss of energy. Should mean that position differences get smaller as the beam is accelerated.
ASIC	Application Specific Integrated Circuit
BCM	Beam Current Monitor. Measures absolute beam current.
BCM calibration	Determination of pedestals and slopes in plot of BCMs vs the Unser current monitor.
beam feedback	Process of feeding back on measured charge asymmetry and position differences in order to minimize those quantities.  The Hall C IA and PZT and the Hall A IA are used to affect these beam characteristics.
bleedthrough	Bleedthrough, or leakage, describes how photoinjector laser light from the other halls, even our own Hall C  DC laser light, leaks through our slit and winds up in our tof spectrum. We see 499 MHz components under our whole spectrum from this. Typically around 50 nA, but has a horrendous charge asymmetry associated with it.
BLM	Beam Loss Monitor. A BCM or PMT used by MCC to make sure transmission is good.
BPM	Beam Position Monitor- a stripline device with x&y pickup plates or wires to measure beam position.
BPM Calibration	Find the pedestal values of the 4 wires which combine to give the x & y positions of the beam.
BS	See any collaboration member. We're full of it. Sometimes also refers to Beam Studies done by MCC on a quasi-regular basis.
BTA	Beam Time Accounting. (beam counting, er, I mean bean counting).
buddy	system of comparing detectors on opposite sides in order to determine the dead time.
cable jiggling	Done to get rid of error lights on the NA electronics.
Cavity BPM	An RF cavity beam position monitor. Temperature controlled, sensitive, but drifts.
CFD	Constant Fraction Discriminator
CHL	Central Helium Liquifier: supplies 2K liquid helium coolant for the accelerator cavities.
Coil pulsing	Periodically done to kick the beam in x&y at the target, in order to map out the detector sensitivity to position differences.
controlled access	Need to get a key & talk to the MCC to get into the hall. In between restricted access and beam permit.
COO	Conduct of Operations
cut0	The region in the TOF spectra to the left of (earlier than) the pion peak and to the right of (later than) the elastic peak. We're talking the extreme unphysical edges of the tof spectrum, where all we see is the bleedthrough.
cut1, cut2, cut3	The region in the TOF spectra between the pion peak and the elastic peak is divided into 2 regions: an early region (cut1) next to the pion peak, and a later region next to (but not including) the elastic peak. Cut 3 is at times later than the elastic peak. Cut 1,2,and 3 do not include any of the elastic or pion peaks, they are background cuts.
CUE	Common User Environment: the JLab computing group's term for our JLab computing environment.
DAQ	Data AcQuisition system
DMCH	see DMCH16X
DMCH16X	Discriminator Meantimer time digital Converter Histogramming 16 channels vXi, in other words, the French electronics (tdc+)
DNL	Differential Non-Linearity: unfortunate fact that each bin in the tdc spectrum is a different width (in time), and that width is a function of time. And we don't know the function, so we have to measure the bin widths regularly with "grey" noise.
DSP	Digital Signal Processing
empty target	Target is in the "in-beam" position, the beam is hitting the target windows, but the LH2 has been replaced with H2 gas at around 30K.
Energy modulation	Maps the detector sensitivity to changes in the beam energy. Not sure how this is actually done….
EPICS	Experimental Physics and Industrial Control System software.
EPLD	Erasable Programmable Logic Device
ESAD	Experiment Safety Assessment Document
ESR	End Station Refrigerator: supplies the Halls with 4K and 15K helium coolant for magnets and targets.
fast feedback
flyswatter	A 30mil thick Al target we could insert just downstream of the H2 cell. It's broken now.
FOPT	Studies Chao has been doing to optimize the adiabatic damping factor. An emmittance measuring tool (involves harp scans).
frame target	Using the 3.2mm thick aluminum frame of the dummy target holder as a target.
French spikes	Feature that occasionally show up in the TOF spectra for the French electronics.  Characterized by one or more tall, narrow (one channel wide) peaks in one or more TOF spectra.  Stopping the run and restarting it appears to cure the problem.
FSD	Fast ShutDown. Shuts down beam in less than 5us to all 3 halls if set. It's an OR of many inputs like target motion, ion chamber thresholds, etc.
Genex	French white noise box for DNL.  Only one DMCH can be measured at a time.  Slower than using the green blocks for this purpose.
GMS	Gain Monitoring System: a laser or flashlamp driven system of optical fibers that can deliver light pulses to the light guides of the G0 detectors for calibration purposes.
GUI	Graphical User Interface. The silly things on our computer screens we click on and work with.
halo monitor/target	A frame with 2 holes (6 & 11mm diameter) on a harp mechanism on the short (new) girder just upstream of the G0 (long) girder. Used to make an absolute measurement of the beam halo.
happyreaper	Program that copies our data to the silo.
Harp scan/swipe	Moving a set of (usually 3) wires across the beam to measure the beam position and profile.
Herbert's paddle	Refers to a scintillation counter paddle sitting on the ferris wheel platform. This guy is just a simple, hard to break or mis-interpret measure of rate in the vicinity of the detectors from beam-tgt interactions. Presently registers about 3uA of anode current (shown on the counting room TV) for 40 uA of beam on LH2.
IA	Intensity Attenuator: device/cell in the injector to affect our charge asymmetry: the difference in beam current between helicity states. It changes the intensity of laser light that hits the photocathode.
IA cell	Injector suite of devices to affect the IA at 30 Hz. Components are an upstream & downstream linear polarizer, lambda/4 or lambda/10 waveplate, Pockels cell, attenuator.
IA scan	To calibrate the IA cell  so that the feedback system can effectively reduce the charge asymmetry. So like changing the intensity deliberately and measuring the helicity correlated charge asymmetry with our BPM.
IHWP	Insertable half-wave plate: used to purposefully flip the polarization of the beam, usually on a time scale of a day or two.
Injector	Just a placeholder for the link to the songsheets.
IOC	Input Output Controller: a computer on a card that talks to our equipment.
Ion Chambers	Used to protect our equipment from excessive radiation due to, eg, a steering problem.
LCW	Low Conductivity Water: deionized water used for cooling at the lab.
leakage	see bleedthrough above.
LEM	Linac energy management software system to set RF gradients.
lock	Usually applies to the situation where a magnet's current is locked to a certain value. If the current is changed, like to better center our beam, the lock will pull it back to where it was over a time of ~10 seconds or so.
LTD	Latching Time Digitizer: the North American tdcs.
MCC	Machine Control Center, phone x7046 or 7047. Crew chief is 7045.
MEDM	Motif Editor Display Manager software used to look at EPICS stuff. Our main MEDM interface to the accelerator is through Monticello.
Moeller	The Hall C polarimeter, measures electron-electron scattering from an iron foil with saturated  polarization in a solenoid field.
MPS	Machine Protection System: includes FSD, BLM, etc. systems.
MPS	Macropulse: Time (~1/30s) during which helicity state is constant.
Munger box	A goofy way of saying a splitter. Try signal distribution.
Musson box	The YO is essentially the TDC start signal, but fine-tuned (using the Musson box) to reflect the true arrival time of the electron bunch in the hall, just before the target, independent of path length (etc.) through the machine.
NPN	Next Pulse Neutralization
Operational restrictions	Beam current limits for different targets, conditions, etc.
OSP	Operating Safety Procedure. Also have Temporary ones (TOSP).
OTR	Optical Transition Radiation viewer, lets you see the light emitted as the particles go from vacuum into a foil.
PD	Program Deputy: MCCs liaison to us and our RC. The PD cell phone number is: 876-7997.
PID	Proportional Integral Differential: a feedback or control scheme in common use here at JLab. P for step size response. I for steady state error. D controls settling time/stability.
Pita voltages	Voltage applied to the Pockel's cell to adjust the circular polarization of the laser. Affects the beam polarization too of course.
PLC	Programmable Logic Controller: a computer & IO device that talks to hardware.
PMT	Photo-multiplier tube.
pulsed beam	Also called tune beam. 1.525% duty factor. 250us on, 100us off, 4.2us on, all this repeated at 60 Hz. DF=254.2us*60Hz. Note 254.2us=1 macropulse. Note 1 micropulse < 2ps.
PZT	Piezo-electric transducer. A mirror whose angle can be changed by application of a voltage at 30 Hz in order to try and null out helicity correlated position differences at our target to the nm level.
PZT scan	To calibrate the PZT mirror so that the feedback system can effectively reduce the position differences. So by varying the voltage applied to the mirror, we measure the helicity correlated position differences with our BPMs.
QE	Quantum efficiency of the photocathode. Ratio of electrons produced per incident photon.
raster	Magnets just at the entrance to the Hall which smear out the beam over the target in order to reduce boiling. G0 uses a square, uniform raster 2mm by 2mm.
RC	Run Coordinator: our liaison to MCC, and collaboration focal point for 2 week stints during the expt.
restricted access	The hall is in its most accessible state, truck ramp is nominally open. You don't need to contact MCC in order to get in or out.
RF	1497 MHz/3 halls=499 MHz. And 499MHz/16=31.1875 MHz, or 1/(32.064 ns).
RHWP	Rotatable half wave plate
RHWP scan	Measurements done to find (one of) the RHWP angle(s) that minimizes the charge asymmetry.
RIP scan	Doing the suite of 3 things: the RHWP scan, the IA scan, and the PZT scan.
RWP	Radiation Work Permit. Or could be Rotatable Wave Plate.
SEE	Switched Electrode Electronics: multiplexing system for BPM readout. Other 2 possibilities are 4-channel, or nanoamp (Hall B) style.
service module	The 2' diameter can you see from the outside, that houses the G0 target and its motion mechanism.
Silviu ratio	A ratio of asymmetry widths computed 2 ways: By summing the proton peak yield over time bins considered statistically independent, and by considering the proton peak yield as one big bin. Time variation of this ratio is what matters.
SMS	The Superconducting Magnet System, ie the G0 magnet.
sniper	A PMT HV protection system that will kill the PMT HV if the detector rates get too high, if the SMS goes off, etc. Needs resetting by hand in the electronics room (all the way at the end, red panel, chest high).
Song sheet	Equipment location drawings. Click here for a nice colored pdf version.
SOP	Standard Operating Procedure.
Superharps
target out	Target is physically completely out of the path of the beam.
VESDA	Very Early Smoke Detection Apparatus.
viewer	A BeO plate or OTR foil for viewing the beam shape. Qualitative.
VME	Virtual Machine Extension electronics hardware standard.
VXI	Vme eXtensions for Instrumentation standard.
Wells plot	Plot of measured detector asymmetries as a function of (deliberately varied) charge asymmetry, to characterize the detector sensitivity to the IA.
Wien filter	Rotates longitudinal polarization component without affecting position.
WNFM	White Noise Fanout Module
YO	The YO is essentially the TDC start signal, but fine-tuned (using the Musson box) to reflect the true arrival time of the electron bunch in the hall, just before the target, independent of path length (etc.) through the machine.