Status ECAL Laser Monitoring

ECAL Days Milano January 23nd, 2009January 23nd, 2009

Adi BornheimAdi BornheimCalifornia Institute of TechnologyCalifornia Institute of Technology

for the Laser Monitoring Groupfor the Laser Monitoring Group

Status ECAL Laser MonitoringStatus ECAL Laser Monitoring

23.01.2009 ECAL Laser Monitoring Status - ECAL Days Milano2

Outline

• Data taking & Hardware issues

• Data handling and processing

• Data analysis


ECAL Laser Monitoring Online Data Flow at P5

ECAL

CMS – Mostly ECAL (also DT, TK, HCAL (?))LaserSystem

Global Trigger

TTCci EMTC

Gap Events

Online PCs

Readout Units

Filter Farm

LaserFarm Storage

Managers

Disk Buffer

SM pushes ‘calibration stream’ to T0 and Laser Farm independently.

HLT Like Gap FilterT0


Monitoring Operations in 2008

The monitoring operation in 2008 was a very long commissioning exercise which is ongoing.

Andre reported yesterday on the DAQ related issues with the calibration sequence. The ‘problems’ encountered are a long chain of partly interconnected DAQ issues on various parts of CMS.

The bottom line is : The data taken suffered from a varying degree of corruption. In CRUZETs most of the APD data and all of the PN data was corrupted. Towards the very end (days) of CRAFT we could take good APD and PN data if the physics trigger rate is zero. At the ‘nominal’ 300 Hz physics rate a large fraction of PN data (particular EE) is corrupted, at 600 Hz most PN data is corrupted. Rates are L1 rates !

As of now, we can not monitor transparency change when taking physics data. Aside from the DAQ issues, the magnetic field effect on the laser is the biggest

issue.

The intense relationship between the DAQ and Monitoring team gives reason to hope that we will fix this in the coming months !

The monitoring related M&O tasks had been exercised in CRAFT. Laser on call was challenged by magnetic field induced laser breakage.


Laser Farm Processing

Laser plots

SortingCalibration

data streaming Primitives

Sorteddata

Fastcheck

Monitoring Laser results MusEcal

OMDS

Light checker

Julie Malclès, Marc Déjardin, Federico Ferri, Philippe Gras, Gautier Hamel-de-Monchenault, Patrick Jarry

Laser Farm is a set of PCs almost equivalent to the HLT nodes in the upstairs racks in P5.

Laser Farm operational since CRUZET2, continued reconfiguring, generally worked smoothly.

Laser Farm will be upgraded from 3 PCs (24 nodes), 10 Tb to 8 PCs (64 nodes), ~30 Tb. Towards the end of CRAFT full processing chain worked in real time. The purpose of the Laser Farm is to handle and process the ECAL portion of the

calibration stream and to extract transparency corrections for the offline reconstruction. Ultimately, it is meant to run a predefined algorithm based on the knowledge of systematic effects we have from the test beam.

The Laser Farm is also serving as a real time monitoring device which looks at every calibration event and provides stability information at or close to design precision to the ECAL shifter.


Laser Farm Online Tools

Light Checker MusECAL

Light Checker : Displays status of data streaming and processing. Delay is ~minute for the streaming info. Note : There is several minutes delay of data being delivered to Laser Farm since T0 is served first

MusECAL : GUI which displays the monitoring primitives - root trees which contain the data loaded into OMDS. It also has some ‘analysis’ capabilities : Sliding window history, individual channel, LM, SM distributions etc.

For the EMGR the results (APD/PN ratios) were available 20 minutes after they arrived on the Laser Farm disk. Total delay after data taking ~30 minutes is streaming runs smoothly.

November 21 2008, ~10 am


Online Stability

Very littel data with good PN.

0.8% before correction of the residual systematic effect due to the laser pulse shape width variations.

Start to rediscover known systematic effects.

Online stability can only be provided with good PN data. Plans to include reference APD for the time being.

EB online stability for now as expected.

APD/PN – 1 Channel

Laser Pulse Width


Laser Monitoring Data in OMDSVladlen Timciuc, Francesca Cavallari et al.

Detailed online results get written into OMDS. Was done for all CRAFT data towards the end of CRAFT.

Reading back data yields 38000 subruns (=transparency measurements). Above example needed 6 separate reads from DB due to memory issues. Each one takes ~12 minutes. So far we do not see any DB performance issues.

Barrel data only was written, corresponding to ~500 full EB calibration cycles (72 LM). This corresponds ~180 hours.

This allows to get all the information from the laser farm processing. After proper corrections are in OMDS, they are copied to ORCON/ORCOFF.


‘Offline Stability’Chris Rogan, AB,Julie Malcles et al.

APD/APD_ref : EB-3 eta12,phi10 / eta13,phi11

Using Laser Primitves from the Laser Farm to study ECAL stability offline.

Expected ‘stability’ in the APD/APD_ref distribution for two channels in the same tower : 0.04 %.

For APD/APD_ref we have ~420 transparency measurements over a period of ~250 hours.


More ‘Offline “Stability”’

EB-2 : eta12, phi10 vs eta14,phi11

Rediscovering early test beam mysteries ? Strongly encourage non-experts to look at the data for their studies to provide feedback. Important step to validate concept of ‘known systematic effects’. To understand this testpulse data would help a lot !


Endcap ‘Monitoring Analysis’

Initial motivation was to measure the gain change in the VPTs between 0T and 3.8T. Some VPT parameters are measured on the bench at a fields << 3.8 T. See also Sashas talk.

A strong (~20 %) effect expected as a function of eta and more subtle effects in phi. Since no PN data available, we use simple ratios between APD amplitude of a 0T and a 3.8 T

run. Use average APD amplitude per run provided by the PFG (Jason Haupt). NOTE : The overall scale of the ratio is not too relevant, only the relative across EE. Runs can

be days apart.

APD(3.8T)/ADP(0T) APD(3.8T)/ADP(0T) vs eta

Jan Veverka, AB


EE systematics

Study the variability of the effect by using different 0T and 3.8T runs and by comparing EE+ and EE-.

Overall effect well reproducable. Indications of a slight difference between EE+ and EE-. Indications that average EE stability is OK. Note similarity of the residuals for EE+ between the

two different 0T reference runs.

f0 one of the EE- funtions


EE stability studies 3.8T

Comparing average amplitude from consecutive runs and across larger run ranges. Rediscovering test beam early and recent mysteries ? NOTE : Gain changes scale with 1.0, transparency changes scale with ~1.55 !


Another example


TB 2006 : Half-SM shift

Four consecutive runs from SM16

-.003

0

.003-.003

0

.003-.003

0

.001513061-> 13064

.44 per mille shift

13066-> 13070

-.59 per mille shift

13064-> 13066

Chris Rogan

23.01.2009 ECAL Laser Monitoring Status - ECAL Days Milano16Time [hours]

VP

T/V

PT

(no

rm_

249

)

TB 2007 : EE unpulsed stability


Summary

Laser Monitoring has been commissioned and is operational. DAQ issues need to be resolved to get a fully functioning system.

Laser Data handling and processing has been implemented and excercised. It is now in good shape and is expected to cope with the taks after Laser Farm expansion.

So far, data looks as expected - within its limits.

Offline analysis is starting. It will now become the main focus of the activity.

We need to reestablish the performance of the ideal test beam situation, investigate observed effects.

We need to define a strategy how to cope with the inherit instabilities of the VPTs.

Documents

Status ECAL Laser Monitoring