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Tandem‐accelerator operation requires a source of negative ions. The earliest negative‐ion sources were based on charge exchange of positive ions from a rf or duoplasmatron source. The development of the sputter‐ion source in the 1970’s produced a revolutionary change in the number of negative‐ion beams for Tandem operation. This article will review operational characteristics of sputter‐ion sources coupled to large Tandem accelerators. These characteristics and matching of the ion source to the accelerator are determining factors for the production of useful beam intensities for physics experiments. A new approach using a 2.45 GHz microwave ion source to produce a high‐quality, positive‐ion beam coupled to a charge‐exchange canal is being developed at Chalk River Laboratories, and some results of this development program will be presented. Plans for future development include the investigation of direct extraction of negative ions from a microwave‐driven plasma.

To determine the feasibility and the economic impact of tumour EGFR, erbB-2 and cathepsin-D measurements in women with node-negative breast cancer.Consecutive tumour samples received at a regional steroid receptor laboratory from patients with node-negative breast cancer were evaluated with commercially available kits to determine EGFR, erbB-2 and cathepsin-D levels.All node-negative patients whose tumours were submitted to the steroid receptor laboratory from November 1992 to March 1994 were included (n = 142). A control group of concurrent node-negative breast cancer patients from the London Regional Cancer Centre (LRCC) database were also evaluated to determine the representativeness of our sample.To determine the proportion of patients who were positive for the 3 newer prognostic factors relative to their risk of relapse.We found 75 positive values in 69 patients (48.6%). We demonstrated that each factor identified a different high-risk subgroup. Epidermal growth factor receptor (EGFR) positivity (10 fmol/mg protein) was found in 16.3% of patients, with 19.9% of patients positive for erbB-2 (250 units/mg protein) and 17.3% positive for cathepsin D (70 pmol/mg protein). Between 10% and 23.2% more node-negative patients currently seen in a regional cancer centre could be offered systemic adjuvant chemotherapy based on a single positive new factor.These tumour evaluations are straightforward using material already available in a regional steroid receptor laboratory or on tumour tissue available to pathologists. The economic impact is minimal; the 1995 cost of performing all 3 evaluations is Can$425-616 (US$304-440) per patient treated depending on the number of assays per run. Prospective clinical trials incorporating tumour EGFR, erbB-2 and cathepsin D are feasible and economically viable.

The MP tandem accelerator at the A.W. Wright Nuclear Structure Laboratory, Yale University has been converted to an ESTU tandem with a design voltage of 20–22 MV. The main features of the new accelerator are described and the progress of the conversion is reported. We present the results of the first phase of the tests and outline the future program.

An investigation of the status of electron equilibrium at the surface of a lesion located in an air cavity of the upper respiratory system irradiated with cobalt 60 teletherapy has been carried out. The experimental method consisted of measuring the “build-up” of ionization in a small ionization chamber in a masonite phantom. This phantom had an air volume in the shape of a rectangular parallelepiped constructed so that its dimensions could be varied to cover the anatomical range. The photon beam passed through this air volume before reaching the ionization chamber. The departure of the reciprocal of the ionization build-up ratio (BUR)−1 from unity was measured as the dimensions of the irradiating field and of the parallelepiped were varied. For practical cases encountered in radiation therapy this departure is not greater than 10 per cent, but should be accounted for if allowances for increased beam penetration through air are made.

The use of triton beams from tritiated titanium inserts in a sputter ion source has become a significant part of the McMaster Nuclear Physics programme. Tritium beams have been run on the McMaster University FN Tandem since 1978 on the basis of one scheduled running period per year accumulating a total of over 4000 hours of running time. Beams of up to one microamp are routinely put on target. Procedures for safe maintenance and operation of such a source have been developed, and techniques for handling up to 40 TBq (about 1000 Ci) of tritium have been approved by the Atomic Energy Control Board.