Introduction to the Backgrounds Study in the BEPCⅡ/BESⅢ Dapeng JIN From Experimental Physics Center Mar. 10, 2008

Outline Motivations What we have done in the past year Simulation results What’s next ?

Motivations

Detectors safety : CsI crystals && scintillators Data quality : data taking environment with low detector backgrounds Safety margin for crystals : <500rads/year ~1rad/day.

What we have done in the past year Joint backgrounds study group founded on Jan. 25th, 2007 with the progress of the BEPCⅡ and BESⅢ; Radiation measurements with Pin Diodes, RadFETs, beam-loss monitors, TLDs, OSLs and CR39s; Experimental studies.

Detectors introduction Pin Diode && RadFET Accuracy not good enough => Safety issues. => Simulated steady run backgrounds

Measurements in the first period of run (first half of 2007), large doses during injections; Measurements in the beginning of the second period of run (from Oct. 2007), large doses during injections; Experiments : aim to reduce injection doses Movable masks on the storage ring; Movable masks on the transport lines; Doses distribution in the radial direction && along beam => Background sources to crystals && radiation protections; Doses due to Synchrotron Radiation runs;

Refer to the followings for detailed results : “BEPCⅡ Background Issues: Collimators and Masks” “BEPCⅡ Background Issues: Beam Loss Measurement” “BEPCⅡ Background Issues: Integrated Radiation Measurement  and Radiation Protection” “BEPCⅡ Background Issues: Real Time Radiation Measurement”

Simulation results Synchrotron radiations when colliding; Beam-gas interactions; Touschek effects.

Touschek

Simulations of all kinds of backgrounds above are completed, results are written into the BESⅢ design report; Positions and types of collimators in the storage rings are decided together with the accelerator people; Positions and mechanical sizes of the uranium masks between the SCQs (Super-Conducting Quadrupole) and MDC inner chamber are decided, manufacture is in progress; The simulated backgrounds is safe for data taking.

Uranium masks

Results of synchrotron radiation SR power distribution on the vacuum chambers near the IP

Photons directly hitting the Be beam pipe, through the beam pipe with and without 10m gold.

Photons in the first layer of the MDC with 10 m gold (Horizontal larger)

Beam-gas and Touschek effects Wire rate of the 1st layer of the MDC

Wire rate of the 21st layer of the MDC

Layer rate of the MDC

Cell rate of the barrel TOF(500KeV Threshold)

Cell rate of the endcap TOF(500KeV Threshold)

Relative energy distribution of the barrel EMC crystals

Relative energy distribution of the east and west endcap EMC crystals

What’s next ??? Thanks a lot! Backgrounds : injection with colliding beams; Backgrounds due to steady runs; Radiation protection near && in the IR; Safe interlock between the accelerator && detector; Your suggestions? Thanks a lot!