Run Coordinator Weekly Report EG6 Commissioning October 19-25 Raffaella De Vita.

Run Coordinator Weekly ReportEG6 Commissioning

October 19-25

Raffaella De Vita

Run Plan for the Week• Data Taking at 5.78 GeV

– Runs with different settings of RTPC HV and solenoid field (534 A, 450 A) for running condition

– DAQ tests– Optimization of RTPC FEE Configuration

• Pass Change (51) on Thursday 22nd• Data Taking at 1.2 GeV

– Measurement of elastic scattering on He4 for calibration purpose: electron trigger only, 80 nA @ 50% LT

– RTPC HV scans for choice of optimal condition for detection of alpha particle

Severe Problems:• Power Outage on Tuesday 20th at 9:08 pm:

– Power in the Counting Room maintained thanks to UPS and emergency generator

– Torus and Solenoid ramped down– Loss of cryogenics– Power restored at 10:15 pm– Technicians and System Experts down in the Hall to recover

various system– Recovery work continued till afternoon of Wednesday– Major Failure:

– Target gas control box because of water dripping from higher levels – EC Sector 5 HV mainframe

– Beam restored Wednesday night

Fast and efficient recovery from difficult situation thanks to the hard work of all technicians and system experts

Many thanks to Krister for repairing the target gas control box in record time

Other Problems• Recurring trips of RTPC HV because of high humidity level.

Seem to be connected to air flow from fan used for preamplifier cooling. Problem solved by modifying air pipe direction

• Noise on RTPC signal preamplifier still being investigated• Bad RTPC FECs replaced• Various accesses for DAQ related resets (bonuspc1, ec2)• IC HV power supply• DC trips in R2S2 (low gas flow) and R2S3 (limp gas bag, leak?)• Sniffer alarm because of blown fuse• EC discriminator in sector 1 outer replaced

Beam Quality

• Beam quality has been fairly good both at 5.78 and 1.2 GeV

• Problems noted:– Orbit locks intentionally turned off for a few days by MCC

Orbit locks for restored on Monday– Few detector trips induced by bad beam position after

long trips in the last few days; problem is being addressed

Choice of Solenoid FieldChoice between 534 A and 450 A:• 534 A provides better shielding from Moeller electrons• 450 A gives better efficiency for detection of low

momentum tracks in RTPC

•Measurement of trigger rate, IC rates, DC occupancy and currents indicate the running with 450 A Solenoid current can be sustained up to beam currents of 100 nA or more:

Trigger Rate @ 100 nA: Electron Trigger ≈ 1.2 KHz Neutral trigger ≈ 4 KHz (will be reduced by increasing thresholds)

DC Occupancy @ 50 nA ≈ 1 % IC Rates @ 50 nA < 25 KHz on inner crystals

5.787 GeV @ 50 nA

Electron trigger rate ≈ 600 Hz

RTPC FEE ConfigurationOptimization of ADC (ALTRO chip) settings:• starting point based on BONUS setup• 100 samples/ch at 10 MHz sampling frequency 10 us sampling window• dynamic pedestal subtraction: a variable pedestal is determined for each channel as the average of samples outside the acquisition window • zero suppression for data volume reduction based on glitch filter

Basic detection scheme Final Samples

RTPC Response to source

• Two (Am241) sources installed in the RTPC

• Signal measured in self triggering mode

• Trigger signal from left and right RTPC sides are built as the sum of 16 GEM channels corresponding to the source closest pads

Clear signal (40-80 mV) visible on the scope

1.2 GeV RunningLow energy run for RTPC calibration via the measurement of elastic scattering on He4:

• Elastic scattering cross section higher at low energy and small electron scattering angles

• Electron detected in CLAS• Elastic events selected thanks to over-constrained kinematics (pe↔e)• 4-momentum of recoiling He4 can be calculated from electron variables• Comparison with reconstructed tracks from RTPC allow to perform

calibration and determine resolution and efficiency

Running Conditions:Beam Current : 80-100 nATarget Pressure: 75 psigDAQ rate (Roc Lock mode): 1.0-1.2 KHzDead Time: 50 %Electron Trigger Only: CC x EC (ECtot = 200 mV)

1.2 GeV Running

Event Reconstruction

Elastic Events on He4

RTPC-CLAS Correlations

RTPC DAQ• Running in ROC Lock mode• Implementation of pipeline readout still in progress:

– First tests showed that rate of few kHz can be achieved– Synchronization problems have been observed:

• Trigger is issued and processed by readout controller• Data sampling is performed• Acquired sample are stored in ADC Multi Event Buffer• BUT NO READOUT OPERATION is initiated by the controller

– Reason not understood– Communication with CERN Group to identify and implement a solution is in

progress

Pending Issues• High Frequency noise on the RTPC signal has been observed• Noise seems to be associated with data read-out operation • Noise level is of the order of 10-20 mV but varies in different crates (left side

is more noisy)• May not be a problem for the signal extraction because appears after the

sampling window

trigger samplingwindow

readout starts

Plans for Upcoming Week•Continue data taking at 1.2 GeV till Wednesday•Data for different RTPC HV settings are been analyzed to

choose optimal running condition for 6 GeV•Pass change (1 5) after Tour on Wednesday•Energy change (6.07 GeV) on Thursday

Next Run Coordinator is Eric Voutier