CERN/LEB 98-3 / LEB M7
 
Minutes of the 7th LHC Electronics Board held on 26th February 1998
 
Present: P. Borgeaud, M. Dentan invited for points 3 and 4), Ph. Farthouat excepts points 7 and 8),
L. Foà, G. Hall, F. Lemeilleur invited for points 3 and 4), M. Letheren, 
E. Petrolo, S. Quinton, P. SharpChairman), G. Stefanini, U. Straumann,
S. Watts invited for points 3 and 4).
Apologies:          F. Corsi, F. Formenti, H. Dijkstra, V. Radeka, W. Smith, M. Turala, U. Straumann.
 

1. The minutes of the 6th meeting held on 9th January 1998 were approved.

2. Matters arising from the minutes:

  On the action to organize an LHC Workshop on radiation-tolerant electronics:

It was reported that R. Richter ATLAS) had initiated a small working group including people from ATLAS, CMS and RD49 rad-tolerant electronics) to study the issue of the radiation-tolerance of power supplies and whether they could be safely located in the cavern. In this context it had been decided to organize a common workshop in May.

Concerning the radiation-tolerance of the wide range of Commercial-Off-The-Shelf COTS) components planned to be used in the experiments, the Board noted an increased awareness of the issues in the LHC Collaborations due to the work of RD49. A number of changes to the electronics systems architectures of some detectors had been made. However, the Board was concerned about the rate of progress in establishing adequate risk management policies and defining clear qualification procedures for assuring that components could safely be located on-detector and in the cavern. This concern was linked to the general problem of disseminating awareness of important results from specialized R&D groups throughout the Collaborations and the difficulties of organization and management of large, distributed Collaborations.
 

3. RD29 - Intermediate Oral Report on the Status of DMILL Stabilization at MHS by M. Dentan, Saclay)

The Board heard an intermediate oral report from M. Dentan on the status of the transfer of the radiation-hard DMILL technology from CEA-LETI to the integrated circuit manufacturer MHS. The technology transfer to MHS will be formally accepted by the DMILL Consortium once the process has been completely stabilized, i.e. when it has been shown on a statistical basis that certain process parameters remain within a specified range of values, both before and after irradiation, and that these results are reproducible. Good progress has been made with the stabilization of the process at MHS, and batches of four different LHC ASICs have now been manufactured and are being evaluated by their design groups.

These DMILL ASIC designs were found to be functional, with most process parameters lying within the specified min-max range before and after irradiation. However, after production of some 25 batches it was found that two parameters needed further optimization to ensure that their statistical distributions are well centered in the allowed range. MHS is now in the final stages of optimizing the process and it is anticipated that final stabilization and acceptance of the technology transfer will be achieved in April or May 1998.

M. Dentan reported measurements made at CERN that showed only a small low dose-rate effect in the DMILL bipolar devices; however these measurements were necessarily made at dose-rates that are much higher than the typical LHC dose-rates. In order to permit these studies to be carried out at realistic LHC dose-rates in reasonable time, the CEA is developing a protocol for accelerated evaluation of the low-dose rate effect isochronal annealing). M. Dentan described a method of making accurate yield predictions. He also recommended that all DMILL designs should undergo a review with the manufacturer in order to optimize the robustness of the circuit design and to ensure optimal yield. 

The Board thanked the DMILL Consortium for its very thorough and professional work, and requested the submission of a final written status report as soon as the technology transfer has been formally accepted.
 

4. RD48 - Oral Report on the 3rd ROSE Workshop on Hardening of Silicon Detectors
    by S. Watts, Brunel University)  

S. Watts reported on the workshop organized by the RD48 Collaboration at DESY on 12-14 February 1998. One of the main new results was the surprise that detectors built from oxygenated float-zone silicon prepared by ITE Warsaw) did not show the expected improvement in radiation-hardness under neutron irradiation. It is thought that this may be due to the process used to oxygenate the silicon - oxidation of wafers followed by diffusion at high temperature. It is believed that in order to improve the hardness, the oxygen must be introduced into the silicon in the position of interstitials; the high temperature processing may have caused the oxygen to become substitutional i.e. to replace a displaced silicon atom in the crystal lattice) or to precipitate out. The silicon manufacturer ITME also located in Warsaw) has now produced samples of oxygenated silicon by another process - directing a jet of oxygen onto the ingot during the float-zone process. This process is expected to introduce the oxygen in the desired interstitial position. Detectors are being fabricated from the new samples and will be irradiated shortly. Silicon with tin is also expected to show improved hardness and detectors are currently being made from silicon-tin material for irradiation in the coming months.  

S. Watts pointed out the incompatibility between the time-scale for the RD48 development of hardened silicon and the start of construction of the detectors. He recommended that construction start with the outer layers, and for optimal hardness these layers should be built with low-resistivity silicon ~1 kOhm cm). He pointed out that the lead-time for procuring low-resistivity silicon is about 1 year. The inner layers could be constructed at a later date, leaving open the possibility of using hardened silicon developed by RD48 when a manufacturer can be found.
 
The Board encouraged the RD48 Collaboration to continue efforts to make its conclusions and recommendations known to the key persons in the LHC collaborations.
 

  5. Status of Frame Contract for DMILL Procurement

G. Hall reported that good progress was being made in discussions between ATLAS, CMS and CERN SPL division D. Gregorio) on drawing up a draft Frame Contract for the procurement of DMILL wafers. Meetings had also taken place with MHS to clarify certain questions. The goal is to establish a framework that, in addition to defining prices as a function of volume and purchasing profile over a period of years, would also define responsibilities and procedures governing acceptance criteria, the monitoring of the yield and feedback to the manufacturer. It was stressed that a framework contract would define conditions and terms for placing orders; there would be no binding obligation to purchase a specified volume. Similar frame contracts could and should be negotiated with all potential rad-hard manufacturers.

 

6. Status of Preparations for the LEB Workshop Rome, 21-25 Sep 98)

E. Petrolo reported that a call for abstracts had been sent out by e-mail with a deadline of 30 April. The leader of IT division, J. May, had agreed that C. Decosse would again handle the preparation of the Proceedings. The Conference poster has been prepared and a web page has been created http://sunset.roma1.infn.it/LEB98/ ).

It is proposed that the structure of the sessions will be the same as in London plenary sessions on the first and last day; the other days to start with a plenary session and to continue with parallel sessions).

Topics and suggestions for invited speakers:
 
 

-   reliability, QA, maintenance:  LHC Technical Coordinators
-   Low- and High-Voltage distribution, 
    Grounding/Shielding/Cooling:
Invited from a running expt. babar, CDF, etc.) 
-   Rad-tolerant electronics: Speaker from RD49
-   Electronics production and test: Invited from outside HEP
-   Electronics for trackers: Review talk across expts.
-   Electronics for calorimeters:                   "
-   Electronics for muons:                   "
-   Electronics for triggering:                   "
-   Optoelectronics and data transfer systems: Invited from outside HEP
-   Slow controls: Consult with LCB
  7. Future Actions of the LEB

The Board reviewed the degree of success it has reached in satisfying its mandate of monitoring R&D, and of identifying and encouraging common developments. The main mechanism used by the Board for fostering communication and common initiatives has been the encouragement via the Electronics Coordinators to set up specialized workshops and working groups, and the organization of the annual LEB workshop. It was also realized that the mailing list for the minutes of the Board needed to be reviewed and extended.

The Board is convinced that the biggest challenge facing the LHC Collaborations is no longer technical, but rather how to manage the engineering aspects of these massive projects in an environment where financial and technical control are distributed, resources are extremely limited and policies can be defined but not enforced. The Board believes that not enough attention is being paid to critical issues such as reliability, testing, and maintenance.

The Board agreed to review these issues again at its next meeting.

8. Any Other Business

The date of the next LEB meeting was confirmed for 30 April 1998.