# Presentation: 295091

## Beam Radiation Simulations in CMS 

- Pushpa Bhat, A. Singh, X. Xia, N. Mokhov
- Fermilab

**August 7 2007**

## Results for:
Normal Operation
pp @ 14 TeV,   L=1034 cm-2 sec-1
Accidental Scenarios
7 TeV protons dumped in TAS 
Other accidental scenarios in progress
Protons lost in tertiary collimators, triplets

- Normal Operation
- pp @ 14 TeV,   L=1034 cm-2 sec-1
- Accidental Scenarios
- 7 TeV protons dumped in TAS
- Other accidental scenarios in progress
- Protons lost in tertiary collimators, triplets

## 14 TeV pp collisions; nominal luminosity (1034cm-2s-1)

- Simulations mostly with DPM + MARS
- Some work with PYTHIA+GEANT for Pixels
- Lots of Results available
- Radiation dose: 2.2 x 10-2 Gy/sec  BPix1
- 				   0.6 x 10-2 Gy/sec other
-   => 1 sec running => 0.22 mGy
- Fluxes at BPix1:
- Charged Hadron Flux: 4.8x107 /cm2/sec
- Neutral Hadron Flux: ~1x107 /cm2/sec
- Muon Flux: 4.5x105 /cm2/sec

## 14 TeV pp

**DPM+**
**MARS**

**PYTHIA+**
**GEANT**

**BPIX**

## FPix

**PYTHIA+GEANT**

## 14 TeV pp

**1 yr = 0.5 * 10****7**** sec **

## Dose (Gy/yr)  yr=0.5E7 sec

**pp**

## Particle Fluxes

## NIEL Fluxes

## Particle Fluxes (pp@14 TeV)

## Dose (Gy/yr) 

**pp**
**1 yr=10****7 ****sec **

## Hadron and Muon Fluxes  (pp)

## Dose (Gy/yr) :  pp @ 14 TeV

**Pixel**

** ****BPIX1  Dose = 0.02 Gy/sec from pp**

**1 yr = 10**7 sec**

## Charged Fluence (pp)

## Accidental Scenarrio7 TeV protons on TAS

- Toy MC to dump (mis-steer) 7 TeV protons onto TAS (~18m from IP)
-  Use MARS for the simulation in the detector

## 7 TeV protons on TAS

## 7 TeV p on TAS

## Radial and z profiles

**EDep**

**Ch. Hadrons**

**Neutral Hadrons**

## 14 TeV pp

**7 TeV protons on TAS**

**For 10****10**** protons on TAS, 5.5 Gy in BPix1 ******** 250 s nominal operation**

## 7 TeV Protons on TAS

- Radiation dose: 5.6 x 10-10 Gy/proton  BPix1
- 4x108 protons on TAS  1 sec pp running
-  but instantaneous rate several orders of magnitude higher.
- 1010 protons produce 5.6 Gy dose <- 250 times pp rate but over a very short time scale
- Total Flux at BPix1: 8.5 x 10-2 /proton

## Summary

- Simulations have been done for pp, beam-gas and accidental loss of 7 TeV protons on TAS.
- For nominal 14 TeV running, radiation from pp collisions is the dominant source.  ~0.02Gy/s at 4 cm radius for nominal running, 5x107 hadrons/cm2/sec
- For protons lost on TAS, radiation dose in BPix1 is 5.6 Gy/1010 protons, fluxes ~ 109/cm2
- Other accidental scenarios (loss of protons in Triplets, TCTs to be studied)

## Extra Slides 

## Hadron Spectra in the Pixel Detectors

**Charged Hadrons /cm****2****/pp collision**

**Neutral Hadrons /cm****2****/pp collision**

## Particle Energy Spectra

**Particle Spectra through BPix1**
**  ****per cm****2**** per pp collision**

**Through Tracker Volume**

**SPM**

## LHC Commissioning 

|  | Commissioning | 1st Year | Nominal | Ultimate |
| --- | --- | --- | --- | --- |
| NpBunch (x1E11) | 1.15 | 0.4 | 1.15 | 1.67 |
| NBunch | 44 | 2808 | 2808 | 2808 |
| * (m) | 0.55 | 0.55 | 0.55 | 0.50 |
| Luminosity (x1E34 cm-2s-1) | 0.015 | 0.12 | 1.0 | 2.3 |
| Events/BX | 30 | 3 | 25 | 52 |
| tBX (ns) | 2021  | 25 | 25 | 25 |
| cross (rad) | 0 | 284 | 284 | 400 |
| luminosity (h) | 15 | 28 | 14 | 8 |
| Bunch length (cm) | 7.55 | 7.55 | 7.55 | 7.55 |
| Ibeam (mA) | 9 | 200 | 580 | 850 |
| Estored/beam (MJ) | 5.7 | 130 | 360 | 530 |

## Collimator Locations

## Silicon Tracker

**TOB**

**TIB**

**TID**

**TEC**

**PIXEL**

**Be-beam pipe**

**SST beam pipe**

**~ 11 Million channels (+66M in Pixel)**

**15000 modules**

**210 m****2**** Si strip sensors**

**Operated at -20****o****C**

## Forward Radiation Shielding

**“****Rotating shielding”**

**Closed (operation)**

**Holes for concrete filling**

**Open (access)**

**“****Fixed iron nose”**

**“****block house” steel frame**

## Tracker in MARS

## Pixels in MARS

- BPix1: r = 4 cm
- BPix2: r = 7 cm
- BPix3: r =11 cm
- z  -30 to +30 cm
- FPix1: |z| = 32.4 cm
- Fpix2: |z| = 46.2 cm
- And there is FPix3
- r from 6 to 15 cm

## Neutron flux from beam-gas 

## Slide 34

## Charged Hadron Flux (cm-2 sec-1)

- Charged Hadron Flux (cm-2 sec-1)

## Slide 36

## Previous Study

**Mika, Nikolai**

## Very high dose rates – several orders of magnitude higher than nominal

**Current results:**
**2.1x10****-2 ****Gy/s**

**Very high dose rates – several orders of magnitude higher than nominal**
**Large particle flux that might lead to component damage **

## Results