general report

Reports

Laser system overview.pdf , bailleux 2009

Lasers in used :

- Diode pump laser DP2, x2, 447nm (1mJ/pulse)

- Ti:S laser pumped by YLF laser, 800 nm (1.48mJ/pulse)

- Diode laser DTL-419QT, 527nm (200 uJ/pulse)

Main specifications of the system with the DP2-2:

Kejun_nss12_laser_2.pdf ; Calor_Liyuan ; DP brochure photonics

The 76,000 lead tungstate (PbWO4) crystals in the CMS electromagnetic calorimeter (ECAL) are radiation hard to high integrated dose, but suffer from dose rate dependent radiation damage. The light Higgs discovery potential is directly related to the energy resolution of the ECAL at LHC, and thus requires precision calibration. The ability to calibrate the crystal calorimeter precisely will be a major factor in determining its ultimate performance. The following 3 aspects are considered: precalibration in a test beam, in situ calibration using physics events and a precise and stable light monitoring system (laser).

2 lasers: one for the crystals ( 447nm) and one for electronic (800 nm). Laser should have enough power to generate light equivalent to several hundred GeV in a few hundreds crystal at time. The light will be transported to the crystals via optical fibers and through 3 levels of distribution. The light from each pulse will be normalized using Si PN photodiodes at each of the levels of distribution.

Laser for crystals: inject light pulses into each individual PbWO4 crystal to measure the optical

transmission near the scintillation spectrum peak (~500nm), and occasionally, as a cross check (700nm).

The red laser 800nm is used time to time to study the wavelength dependency of the transparency corrections.

3 levels of distribution: a light source and high-level distribution system which sends pulses to a

selected calorimeter element (1/2 barrel supermodule or endcap), and a 2-level distribution

system mounted on each calorimeter which delivers the pulses to the crystals.

The system is designed to continuously monitor the calorimeter in one of the 2 operational modes:

- Continuous in-fill mode (during 3 us gaps every 88,924 u sin the LHC beam),

- Stand-alone monitoring (outside LHC fills to follow the recovery of the PbWO4 crystals)

To meet the stringent requirements on the light monitoring precision and stability a new commercial diode-pumped blue laser ("DP2-447") has been commissioned and installed at CERN for the 2012 operation of the CMS ECAL (TiS laser before) The laser unit has a simple structure and is expected to be more reliable than the existing lamp-pumped lasers used by the monitoring system. The stability of critical quantities such as the intensity, width and timing, is better than that of the lamp-pumped lasers.

2019

CMS LSO safety new barrack CMS_LSO_LS2.pptx

ETN from Photonics Q19-0815CX - 11-381 DP2-ETN.pdf

OM meeting Laser maintenance August Laser maintenance_August2019.pptx

ECALdays B.Lenzi Monitoring Upgrade BL_LMupgrade_ECalDays_2019_05_22.pdf

ECAL days Laser correction UltraLegacyTags_ECALdays_Zurich.pdf

Dave Cockerill EE power - Laser scan laser-power-vs-pn-data.pdf

Long fibre Test - report Long fiber test_2.pptx

2018

integration forum, 15 Jan laser_room_15Jan2018.pdf

long fibre test Long fiber test_20March.pptx

USC barrack integration USC_CO2_Cooling_Room_Ph2 Copy.pdf USC_Control_room_Ph2.pdf