Highlights on the TOSTER Project
(TOtem STrip Edgeless Radiation hard detector)
CERN-Intas project
INTAS Institutes:
NIS Institutes:
Gennaro Ruggiero
TOTEM Week
Collaboration Meeting December‘08
The TOSTER Project
Project started in July 2006
Based on a working plan agreed by all institutes before the approval of the project
In 2.5 years 6 workshop have
taken place, all the work done in
this framework presented at
these workshops
Most of the relevant information
available in a protected area of
the RP website
Where have we started
• At that time our own Edgeless detectors where already going to
production...
– First tests on edge efficiency
– Reliable and solid technology
• We have been the first to use silicon detectors with our special
biasing scheme and several questions where open
– Not fully understood electric field at the edge
– Radiation hardness studies only started.
• We did not know how our biasing scheme that separates and
terminates surface current form the bulk current could work after
high irradiation and moreover how to apply this biasing scheme to
RadHard Si Detector Technology
Development of tools for study
At the start of the project we had to develop methods for
the direct measurement of potential drop across the
edge
• Microprobe and OBIC (Bologna)
• TCT (St. Petersburg)
but also
Microprobe
• SEM (Lappeenranta)
A lot of data produced and methodologies and results compared.
Microprobe turned to be the most effective methodology although OBIC
and TCT gave similar, but less precise results. SEM could have been
also very effective but unfortunately during the project this SEM could
not be pursued due to logistic problems in Lappeenranta
Measurements, Simulations
Modelling to new (Mask) Design
• From the measurements, at high fluence the decoupling
surface-bulk current might not be anymore effective on our
p+-n detectors
• In must be said that the p+-n is not rad hard, while n+-p is
(more complicated but) rad-hard detector technology
• Same reasons of limiting the edgeless p+-n at high doses
would stabilise the edgeless performance for the n+-p
technology
Mask design and 1st test samples
MCZ p-type Si, Processed at RIMST, n+p with edgeless design exploiting the CTS principle
Layout: 10 different designs
EPCT 140_1s, non-irradiated
1.0E-03
Current (nA)
1.0E-04
1.0E-05
pad
CTR
1.0E-06
total current
1.0E-07
1.0E-08
1.0E-09
1
1 –pad, regular
2 –pad, regular
3 –strip, n20/p10, n60/p10, regular
4 –strip, n20/p20, regular
5 –EDL strip, n20/p20, 170, cut through
6 –EDL strip, n20/p20, 170, non cut
7 –EDL pad, 85, cut through
8 –EDL pad, 105&115, cut through
9 –EDL pad, 140, cut through
10 –EDL pad, 170, cut through
10
100
1000
Voltage (V)
The CTS principle holds also on n+p technology !!!
Irradiations and First (IV) tests
Many samples (>>100!!!) with different edge configurations have been irradiated
in this last irradiation run at CERN (Many thanks to Federico and William!!!) up
to fluences of 3*10^15p cm. The testing has started (Vladimir and Elena) but
not finished (activation at the high doses).
The currents seems to be decoupled...
Surface current
Pad (bulk) Current
EPCT 140
pad current
EPCT 140
CTR current
1.0E-02
1.E-03
1.0E-03
1.E-04
1.0E-05
140-1s, non-irradiated
1.0E-06
1194 140-10, 1.19e14 cm-2
1.0E-07
1186 140-4, 4.53e14 cm-2
1.0E-08
1196 140-11, 6.85e14 cm-2
Current (A)
Current (A)
1.0E-04
1.E-05
140-1s, non-irradiated
1194 140-10, 1.19e14 cm-2
1.E-06
1186 140-4, 4.53e14 cm-2
1196 140-11, 6.85e14 cm-2
1.E-07
1.E-08
1.E-09
1.0E-09
1
1
10
Voltage (V)
100
1000
10
100
Voltage (V)
1000
Conclusions
• If we envisage to have rad-hard edgeless si detectors
this would be the line to follow.
BUT...
• This project is coming to an end. We will have to
deliver a final (the 3rd one) report by the end of April
2009.
• The people part of this consortium is still interested
in working on this development. Nevertheless there
would be no frame binding these groups together.