T. Pinelli

Total cross section measurement for the three double pion photoproduction channels on the proton

Abstract The total cross sections for the three γp → Nππ reactions have been measured for photon energies from 400 to 800 MeV. The γ p → p π 0 π 0 and γ p → n π + π 0 cross sections have never been measured before while the γ p → p π + π − results are much improved compared to earlier data. These measurements were performed with the large acceptance hadronic detector DAPHNE, at the tagged photon beam facility of the MAMI microtron in Mainz.

Measurement of the E2/M1 ratio in the N ---> Delta transition using the reaction p(gamma(pol.),p)pi0

The small electric quadrupole E2 amplitude of the predominantly magnetic dipole M1 p -> Delta(1232) transition has been measured using 270 to 420 MeV tagged linearly polarized photons in the p(gamma,p)pi0 reaction at the Mainz Microtron MAMI. Differential cross sections and photon asymmetries were determined by measuring the recoil proton in the cylindrically symmetric 4pi detector DAPHNE. From the proton angular distributions the ratio E2/M1 = -(2.5+-0.2+-0.2)% at the maximum of the Delta(1232) resonance has been derived.The small electric quadrupole E2 amplitude of the predominantly magnetic dipole M1 p{r_arrow}{Delta}(1232) transition has been measured using 270 to 420MeV tagged linearly polarized photons in the p({gamma}{searrow},p){pi}{sup o} reaction at the Mainz Microtron MAMI. Differential cross sections and photon asymmetries were determined by measuring the recoil proton in the cylindrically symmetric 4{pi} detector DAPHNE. From the proton angular distributions the ratio E2/M1=-(2.5{plus_minus}0.2{plus_minus}0.2){percent} at the maximum of the {Delta}(1232) resonance has been derived. {copyright} {ital 1997} {ital The American Physical Society}

Clinical lessons from the first applications of BNCT on unresectable liver metastases.

After a long series of studies on the effects of neutron irradiation of 10 B loaded neoplastic cells both in culture and in animal experiments, we started the clinical application of BNCT on humans affected by liver metastases of a radically resected colon adenocarcinoma. The procedure we adopted includes a first surgical phase, with hepatectomy; a radiotherapeutic phase, in which the isolated liver, washed and chilled, is extracorporeally irradiated with thermal neutrons; and then a second surgical phase for the reconnection of the liver to the patient. Until now two patients have been subjected to the BNCT treatment. The first one survived 44 months with a good quality of life, and died because of diffuse recurrences of his intestinal tumour. The second patient had the same early perioperative course, but after 33 days a worsening of a dilatative cardiomyopaty, from which he was suffering, determined a cardiac failure and eventually death. This clinical experience, although limited, has shown that extracorporeal neutron irradiation of the liver is a feasible procedure, able to ensure the complete destruction of liver metastases and a possible long lasting survival. In our patients neutron irradiation caused massive cellular necrosis highly specific to tumour cells, whereas normal cells were mostly spared. Nevertheless, the impact of such a traumatic operation on the patients organism must be taken into account. Finally, we have to be aware that the fight against tumour rarely leads to a complete victory. We now have an innovative weapon which is both powerful and partly unsettled: it must be refined and above all used.

DAPHNE: a large-acceptance tracking detector for the study of photoreactions at intermediate energies

Abstract A large-acceptance (94% of 4π sr) hadron detector capable of handling multiparticle final states is described. The track reconstruction capability, energy resolution, particle identification capability and neutral-particle detection efficiency of the detector are discussed and the results of tests shown. Tests have been performed both with cosmic rays and in a realistic experimental situation using a 500 MeV photon beam impinging on hydrogen and deuterium targets.

Neutron autoradiography imaging of selective boron uptake in human metastatic tumours

The ability to selectively hit the tumour cells is an essential characteristic of an anti-tumour therapy. In boron neutron capture therapy (BNCT) this characteristic is based on the selective uptake of (10)B in the tumour cells with respect to normal tissues. An important step in the BNCT planning is the measurement of the boron concentration in the tissue samples, both tumour and healthy. When the tumour is spread through the healthy tissue, as in the case of metastases, the knowledge of the different kinds of tissues in the sample being analysed is crucial. If the percentage of tumour and normal tissues cannot be evaluated, the obtained concentration is a mean value depending on the composition of the different samples being measured. In this case an imaging method that could give information both on the morphology and on the spatial distribution of boron concentration in the sample would be a fundamental support. In this paper, the results of the boron uptake analysis in the tumour and in the healthy samples taken from human livers after boron phenylalanine (BPA) infusion are shown; boron imaging was performed using neutron autoradiography.

Two-body photodisintegration of the deuteron from 100 to 800 MeV

Abstract The total and the differential cross sections for the D(γ,p)n reaction have been measured over the photon energy range 100-800 MeV at the 855 MeV MAMI Microtron in Mainz. Using the large acceptance detector DAPHNE in conjunction with the Glasgow tagging spectrometer, high precision results with small systematic errors were obtained. The data are presented in the form of thirty-five angular distributions at c.m. proton angles between 30°–160° in 10° intervals and at photon energies in steps of 20 MeV. Previous experimental work is reassessed in the light of the present results and comparison with some recent theoretical calculations.

A compact solid-state detector for small angle particle tracking

MIDAS (MIcrostrip Detector Array System) is a compact silicon tracking telescope for charged particles emitted at small angles in intermediate energy photonuclear reactions. It was realized to increase the angular acceptance of the DAPHNE detector and used in an experimental program to check the Gerasimov-Drell-Hearn sum rule at the Mainz electron microtron, MAMI. MIDAS provides a trigger for charged hadrons, p/� ± identification and particle tracking in the region 7 ◦ < # < 16 ◦ . In this paper we present the main characteristics of MIDAS and its measured performances.

A range telescope technique for particle discrimination and energy reconstruction

We present an analysis technique (“range method”) that optimizes particle discrimination and enables energy reconstruction using a sampling detector. The method is a powerful extension of the well known dEdx - E technique in which the energy loss rate measured by several scintillator layers is fitted on the theoretical energy-range curves. The general features of the method will be discussed and its application to nuclear physics investigations at intermediate energies with the DAPHNE detector. Momentum reconstruction for protons with a resolution of ΔPP = 2.5−10% (FWHM) in the range P = 300–900 MeV/c has been obtained.

Study of three-nucleon mechanisms in the photodisintegration of 3He

Abstract The cross section of the 3He(γ,pp)n reaction has been measured for the first time over a wide photon energy and proton angular range (200 MeV ≤ Eγ ≤ 800 MeV; 20° ≤ ϑplab ≤ 160°) using the large acceptance detector DAPHNE at the tagged photon facility of the MAMI microtron in Mainz. The wide kinematical coverage of the measurement has allowed a detailed analysis of three-nucleon absorption mechanisms. A model developed by Laget explains the main characteristics of the data in the Δ resonance region.

Two-body photodisintegration of 3He between 200 and 800 MeV

Abstract Differential cross sections for the 3He(γ,pd) reaction at photon energies between 200 and 800 MeV at all proton c.m. angles between 35° and 145° have been measured using the tagged photon beam facility of the 855 MeV MAMI accelerator in Mainz. Reaction products were detected using the large acceptance detector DAPHNE. The results confirm the rapid decrease of forward-angle cross sections with increasing Eγ whilst at backward angles, aided by the high precision of the measurement, we can see a clear enhancement in the angular distribution which is a possible signature of three-body mechanisms.