radiation hard sensors r&d for hl-lhc4 l. uplegger | radiation hard sensors r&d for hl-lhc...

Radiation Hard Sensors R&D for

HL-LHC

Lorenzo Uplegger

Fermilab Detector R&D Program Review

29 October 2014

HL-LHC Requirements

• Luminosity upgrade to 5x1034 cm-2/s-1 → 1500 fb-1 after 5 years

• At 3 cm from the interaction point the radiation fluence of 2x1016 neq/cm2

• Standard planar pixel sensors cannot survive these conditions!

10/29/14 L. Uplegger | Radiation Hard Sensors R&D for HL-LHC 2

Collaboration goals

• Our goal is to test the candidates for the HL-LHC upgrade before and after irradiation to compare the

performances and understand if we have a technology capable of withstanding the enormous fluences.

We are mainly focusing our efforts on three different sensor types:

Diamond sensors

3D sensors

Thin silicon sensors

• Big global effort on Sensor R&D for the HL-LHC

RD42 (diamond)

3D consortium (3D sensors)

ATLAS, CMS and LHCb

• Our collaborators:

3D silicon sensor: Purdue, SUNY, TAMU, INFN Torino

Diamond: Colorado, Tennessee, TAMU, INFN Milano, INFN Lecce, Catania, Strasbourg

Thin silicon: Purdue, Colorado, SUNY

• Test beam at FTBF and irradiation at LANSCE

Fermilab arranged the test beam schedule, organized the test beam plan, shift, and data analysis

and coordinated with Univ New Mexico on the irradiation test at LANL.


CMS pixel technology


• Planar n-on-n technology is currently used for the CMS and ATLAS pixel

detectors

• Charge needs to travel along the 300 μm thick substrate to be collected,

so when the detector is heavily irradiated most of it gets trapped in the

bulk

CMS pixel technology vs 3D


• 3D detectors have the electrodes etched in the bulk so the charge

collection distance is independent from the bulk thickness and different

electrodes configurations can shorten the collection path down to few

tens of μm

• Lower bias voltages, fast collection time, much higher radiation

tolerance



• Regular n-on-n thinned down to 50-100 μm

• Pros: well know technology

• Cons: small charge produced, thinning process not yet mature

• n-on-p from HPK also 50-100 μm

• Pros: charge multiplication layer, higher charge then n-on-n

• Cons: needs coating layer to avoid sparks

Diamond sensors


• Pros:

• Intrinsically rad-hard

• No leakage current -> doesn’t need cooling when irradiated!!!

• Cons:

• High band-gap generates less charge than silicon

• Bulk polarization effects in high intensity environments

R&D effort at FNAL


• All samples are tested in the 120 GeV beam at the FTBF facility before

and after being irradiated at LANSCE

FNAL test stand


• Test stand at Feynman computing center to test irradiated and not

irradiated sensors with calibrations and radioactive sources

Test beam results with 3D sensors


• In the last few years we tested several 3D devices from different vendors.

We have been able to determine that the most favorable design is the

one with 2 electrodes

• Good quality sensors from SINTEF

Efficiency 94% for not irradiated sensors

SINTEF irradiated sensors and PSI46Analog


• Efficiency on cell: average efficiency = 93.2%

• Slightly lower than the un-irradiated, as expected!

FBK 3D sensors before and after irradiation


• Seven 3D sensors bonded to CMS PSI46dig ROCs were tested at the FTBF in

April 2014

• One died during the trip back to Italy, the remaining six have been irradiated at KIT

(Karlsruhe institute of technology) in June at fluences of 1-3-6 x 1015 neq/cm2. The

two ROCs 6 x 1015 didn't survived.

Sensor Irradiation(neq/c

m2)

Efficiency before

irradiation

Efficiency after

irradiation

FBK_11_37_01 1x1015 98.7% 93.7%

FBK_11_37_03 1x1015 98.8% Died during testing

FBK_11_43_01 3x1015 99.0% 84.6%

FBK_11_37_02 3x1015 99.1% 92.5%

• Efficiencies obtained with the irradiated FBKs are very good, especially if

compared with the one measured for the same sensors bonded to the

PSI4Aanalog chip (below 80% for 1E type).

FBK 3D sensors before and after irradiation


Before Irradiation, Vbias 30V After Irradiation, Vbias 85V

Angle = 0°

Angle = 10° Angle = 10°

Angle = 10°

Single crystal Diamond sensors


• Single crystal Diamond (DDL)

– 4.7 4.7mm2 area (roughly ¼ of the ROC)

– 500 m thickness

– and 508 m CCD

• 100 150 m2 pixel-cells to match CMS readout chip

• ROC threshold at roughly 3.5 ke

• Detector normal to beam (within 2)

• 500V Bias

Single crystal Diamond charge collection


• Average charge collected by the sole pixel pointed by the track

– (a) on a pixel and (b) on the region about the 4-pixel corner

• Charge sharing extends to about 20 m from the edges

– Consistent with 8 m as resulting from convolution of align 7

m and eff_diff 4 m (see following studies)

Polycrystalline Diamond


• Polycrystalline Diamond (from DDL)

– 1 1 cm2 area

– 500 m thickness

– and 172 m CCD

• 100 150 m2 pixel-cells to match CMS readout chip

• ROC threshold at roughly 2.5 ke with a dispersion of about 0.5 ke

• Detector normal to beam (within 2)

• 500V Bias

Polycrystalline Diamond


• Average charge collected by the sole pixel pointed by the track

– (a) on a pixel and (b) on the region about the 4-pixel corner

• Sharing seems to impact signal even at more than 40 m away from

the edges

• Efficiency only 64% due to the high

threshold of the old PSI46Analog ROC

Charge

• Fiducial region to 35 m away from the edges to just limit the sharing without running out of statistics

• MPV 3000 e

– To be compared with

• 0.7 36 e/ m 172 m 4300 e, just from measured CCD,

• and roughly 0.8 4300 e 3400 e, to account for undetected signal induction on nearby pixels

35 m

35 m

35 m

35 m

Fiducial area cut

18

Polycrystalline Diamond Landau

3D Diamond sensors


• 3D diamond sensors are an intriguing relatively new development.

• Short collection distance

• Our collaborators from Tennessee will bring some samples for the

November test beam run!



Working in collaboration with SINTEF to try to thin down regular n-on-n

sensors from the FPIX phase I pixel production run.

Conclusions


• Very strong program for pixel sensor R&D in the US closely connected

with the overall CMS effort for Phase II

• Different sensors’ technologies have been evaluated and some

conclusions have already been drawn:

• 3D

sensors preferred configuration has 2 central electrodes

have been tested up to 3x1015 performing as expected

many vendors (FBK, SINTEF, CNM) can produce very high

radiation tolerant devices

• Diamonds:

single crystals perform very well but not good enough for high

intensity environments!

Polycrystalline sensors do not generate enough charge for the

present generation of ROCs

Conclusions


• 3D diamonds:

very interesting technology but still needs to be proven feasible

• Thin silicon:

Works both for epitaxial and regular n-on-n sensors but for

thicknesses of about 50-100um needs a new generation of

ROCs with much lower thresholds

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