Radiation Doses in CBM -Radiation Doses in CBM -A first estimate and anA first estimate and anassessment of assessment of

consequences consequences Walter F.J. Müller, GSI, Darmstadt

11th CBM Collaboration Meeting26 February 2008

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 2

Gray – Mrad – Particle FluenceGray – Mrad – Particle Fluence

1 Gy = 100 rad = 1 J/kg 1 J = 1 VAs = 1 CV → 1 eV = 1.6·10-19 J dE/dx(mip,si) = 1.67 MeV/(g/cm2) [PDG] 1 mip/cm2 ↔ 1.67 MeV/g = 2.67·10-9 J/kg

This leads to the often used relations:1 Gy ↔ 3.75·109 mip/cm2

10 krad ↔ 3.75·1011 mip/cm2 1 Mrad ↔ 3.75·1013 mip/cm2

Note: For lower energy protons (typ. Cyclotron energies) the relation is changed due to higher dE/dx, e.g. 160 MeV p: 1 Mrad ↔ 1.47·1013 mip/cm2

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 3

CBM-Year and CBM-Lifetime CBM-Year and CBM-Lifetime

To estimate lifetime doses an operating scenario has to be assume. For CBM the current key numbers are:

CBM-Year ↔ 5·106 sec at 100% duty cycle Note: 1 yr = 3.156·107 sec 1 CBM-year ↔ 2 month at 100% duty cycle

↔ 4 month at 50% duty cycle

CBM-Life ↔ 6 CBM-Year @ full intensity CBM-Life ↔ 3·107 sec at 100% & full intensity

full intensity ↔ 107 Au+Au interactions/sec

CBM-LifeCBM-Life ↔ ↔ 33··10101414 Au-Au min. bias interactions Au-Au min. bias interactions

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 4

TTotal otal IIntegrated ntegrated DDose in CBM-ose in CBM-LifetimeLifetime Reference system is Au+Au @ 25 A GeV central

collisions Hit densities are given in hit/cm2 per central Au-Au For an estimate of a lower limitlower limit of the TID

assume multiplicity(min. bias) = 0.25 · multiplicity(central) assume particles are MIP hadrons

1 hit/cm2(cent) → 0.25 hit/cm2

(min.bias)

→ 7.5·1013 part/cm2 over CBM-Life→ 2 Mrad over CBM-Life

For rough lower limit estimatesrough lower limit estimates:1 hit/cm1 hit/cm22 ↔↔ 2 Mrad in CBM-Life 2 Mrad in CBM-Life

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 5

Some ValuesSome Values

Use hit densities form CBM Technical Status Report2006 Update, Section 13.1 "Hit densities and Rates"

Detector edge hit/cm2 part/cm2 TIDSTS @ 30cm inner 10 7.5·1014 20 Mrad

outer 0.25 1.8·1013 0.5 MradSTS @ 1m inner 1 7.5·1013 2 Mrad

outer 0.03 2.3·1012 60 kradTRD @ 4m inner 0.04 3.0·1012 80 krad

outer 0.002 1.5·1011 4 kradTOF @ 10m inner 0.01 7.5·1011 20 krad

outer 0.0006 5.0·1010 1.2 krad

STS @ 30 cm is now 1st plane in 'all strips' configuration(the hit rate for STS@30 cm is scaled from the STS3 @ 20 cm plot of the CBM TSR)

Hit rates in 1st MUCH plane are similar to STS plane @ 1m

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 6

Consequences 1Consequences 1

STS sensor inner part 1st plane (20 Mrad) beyond LHC-style designs

(CMS Si-tracker designed for 1.6·1014 part/cm2 or 6.7 Mrad; NP B78(1999)322)

→ inner part of 1st plane may need replacement

CBM-XYTER > 50 Mrad demonstrated many times for rad-hard

designs STS perimeter (1 MRad) and MUCH 1st plane center (2

Mrad) → some 'rad-hard lite' design might be ok.

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 7

Consequences 2Consequences 2

COTS (CCustom-00f-TThe-SShelf) components many COTS components are known to fail at 20-100 krad some fail, e.g. bipolar transistors, can fail at 1 krad and are

sensitive to displacement damage, thus neutron flux A very preliminary very preliminary COTS usage policy:

TID < 1 krad: selected COTS equipment can be usede.g. crates, power supplies ect.qualification done on the equipment level

TID < 20 krad: qualified COTS components can be usedqualification done on the component level

This divides the Cave in 3 Zones. Examples TOF perimeter (1.2 krad) → COTS equipment TOF center (20 krad) → COTS components STS whole assembly → no COTS possible

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 8

Cave Layout - OldCave Layout - Old

Cave – Side View

Magnet MUCHBeamdump

Step in Floor, dividing cave in CBM and HADES sector No shielded area close

to STS and MUCH

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 9

Cave Layout - NewCave Layout - New

Cave – Side View

No 'Step' anymore Shielded area forelectronics ect.

Extra Shielding

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 10

Cave Layout - NewCave Layout - New

New space foelectronics andother services

Shielding Drawing: W. Niebur

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 11

Cave Layout – Cable path lengthCave Layout – Cable path length

Cable path length from STS/MUCHabout 10 m

5.7 m

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 12

Cave Layout – First FLUKA Cave Layout – First FLUKA CalculationCalculation

Cave – Side View

FLUKA by D. Bertinidone for 50 cm shielding

If correct, more than 50 cm shielding

needed

preliminary !!!!

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 13

TID and COTS TID and COTS SEU SEU

Assume COTS parts are used at 20 krad 'places' 20 krad ↔ 0.01 hit/cm2

(cent)

↔ 2.5·104 part/(cm2·s) [ @107 int/s ] Typical SEU (SSingle EEvent UUpset) cross section for

SRAM cells: 3·10-14 cm2/bit [refs see next slide]

Typical SEU is a SBU (SSingle BBit UUpset): one bit toggles 0↔1 Rate of SRAM SBU's

7.5·10-10 SBU/(bit·s) 7.5·10-4 SBU/(Mbit·s) 2.7 SBU/(Mbit·hour)

20 krad 20 krad ↔↔ 2.5·10 2.5·1044 part/(cm part/(cm22··s)s)20 krad 20 krad ↔↔ 2.7 SBU/(Mbit 2.7 SBU/(Mbit··hour)hour)

Note: Neutronsare likely to dominate !

!! This is a lower limit !!!! This is a lower limit !!n contribution mightn contribution mightbe 10 times higherbe 10 times higher

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 14

SRAM SEU Cross SectionsSRAM SEU Cross Sections

SRAM cells in FPGA configuration memories:

Denes et al, Proc of LECC-2006 ALTERA & ACTEL devices:

3-11·10-14 cm2 for embedded SRAMs 0.3-8 ·10-14 cm2 for LE Flip-Flops

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 15

SDRAM SEU Cross SectionsSDRAM SEU Cross Sections

SRRAM SEU Cross Sections vary much more 64 MBit ISSI IS42S16400 3·10-17 cm2/bit

Bunkowski et al, NIM A532(2005)708 512 Mbit 'Manufacturer C' 4·10-19 cm2/bit

512 Mbit 'Samsung' 4·10-17 cm2/bit Langley et al., Proc. of IEEE Rad.Eff.Data Workshop 2003

128 Mbit Micron MT48LCM32B2 2.8·10-16 cm2/bit Hiemstra et al., Proc. of IEEE Rad.Eff.Data Workshop 2007

Again, assume '20 krad' places:

20 krad20 krad ↔↔ 0.036 SBU/(Gbit 0.036 SBU/(Gbit··hour) for 4hour) for 4··1010-19 -19 cmcm22/bit/bit↔↔ 3.6 SBU/(Gbit 3.6 SBU/(Gbit··hour) for 4hour) for 4··1010-17 -17 cmcm22/bit/bit

Note: Neutronsare likely to dominate !

!! This is a lower limit !!!! This is a lower limit !!n contribution mightn contribution mightbe 10 times higherbe 10 times higher

26 February 2008 11th CBM Collaboration Meeting -- Walter F.J. Müller, GSI 16

The EndThe End

Thanks for Thanks for your attentionyour attention