# Development of diamond-based detectors for high-intensity pulsed beam monitoring

R Molle, M-L Gallin-Martel, C Koumeir, J L Bouly, J Collot, D Dauvergne, T Durand, P Everaere, L Gallin-Martel, A Guertin, et al.

► To cite this version:

R Molle, M-L Gallin-Martel, C Koumeir, J L Bouly, J Collot, et al. Development of diamond-based detectors for high-intensity pulsed beam monitoring. SBDD XXVI Hasselt 2022, Mar 2022, Hasselt, Belgium. hal-04839747

HAL Id: hal-04839747

https://hal.science/hal-04839747v1

Submitted on 16 Dec 2024

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Distributed under a Creative Commons Attribution 4.0 International License
## Online dose control in hadrontherapy

The treatment of tumors by light-ion beams is an innovative cancer therapy known as hadrontherapy. Energy deposition by ions can be modelized by Bethe-Bloch formula, which predicts a maximum of energy deposition, the **Bragg peak**. Series of incident beams of different energies and intensities are used to form a so called Spread-Out Bragg Peak (SOBP). It allows an efficient treatment on all the Planned Targeted Volume. Moreover, recently it was discovered that the use of high intensity beams is advantageously leading to the so called **Flash effect** (high dose up to 10 Gy in tens of µs in a single fraction). Indeed, tumor cells are less resistant to this type of irradiation than the healthy ones.

In vivo ion range verification is necessary to avoid radiation induced cancer or a lack in the treatment. To do so, secondary particle detectors, that surround the patient, and a beam monitor are coupled. Time-of-flight (TOF) techniques are used to permit background reduction and secondary particle of interest, namely prompt gamma, for better selection.

In ANR-DIAMMONI, diamonds are studied as beam monitors, placed upstream of the patient, taking advantage of intrinsic diamond properties such as fast timing, low leakage current and radiation hardness.

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## ANR-DIAMMONI beam monitors

The DIAMMONI beam monitor is designed for particle counting and time stamp on a wide beam intensity range.

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To satisfy online ARRONAX beam monitoring, two different operating modes are foreseen.

**Bunch counting mode:** (low intensity)

* Single particle counting up to 100 particles per bunch

* Bunch stamp

**Train counting mode:** (high intensity)

* Particle counting in one train

* Train stamp

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Dedicated electronic developments (discrete and ASIC) are foreseen for each counting mode.

Orthogonal strips in x and y will be used as electrode to check the beam profile.

A first prototype will be released in 2024.

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## The ARRONAX Cyclotron

The **ARRONAX cyclotron** (Nantes France) is a 68 MeV ion accelerator.

Beam intensity can reach 20 µA, with proton, deuterium and alpha particles.

In pulsed beam mode, bunches of 4 ns ON and 29 ns OFF constitute trains.

"Train duration"(*dt*) and "inter-train time" (*dit*) are tunable.

ARRONAX is a dedicated tool for a beam monitor development satisfying the Flash therapy requirement.

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## Diamond beam monitor simulation

Development of such a beam monitor should be simulated to optimize geometry

A first simulation tool has been set-up based on COMSOL Multiphysics (meshing and electric field resolution), SRIM (ion path in diamond) and MATLAB

It aims to understand how charge carriers drift in diamond depending the impact point on strips.

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CLaRyS
Single proton hodoscope
developed at LPSC

←ID Synchro
for microbeam
synchrotron radiation
therapy at ESRF beam
monitor prototype

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## Beam tests results with 68 MeV protons in ARRONAX

### Diamond counting capabilities

* **Bunch counting mode:** first investigations with commercial front-end electronics devices :

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P. Everaere PhD Thesis LPSC IP2I Lyon CREATIS

* **Train counting mode:** first results with front-end electronic devices developed at laboratory. The integration is done by a QDC (Charge to Digital Converter).

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<figure><img src="image_17.png" /><figcaption>Arronax set-up</figcaption></figure>

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**Tests on:**

* sCVD diamonds

* 150µm thick

* 540µm thick

* pCVD diamond

* 300µm thick

### Linearity of diamond response with the beam intensity

* Each diamond exhibits a **linear response with intensity**

* sCVDs data do not respect the 0,3 thickness ratio (540 µm vs 150µm)

* Over-biasing improves charge collection

* Polycrystalline respons is worse than the one of single crystals

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### Damaging studies under irradiation

α ($^{241}$Am source) spectroscopic measurements

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* High intensity beams (68 MeV proton) affect charge collection

* A secondary peak appears in lower energies ⇒ signature of incomplete charge collection

* Peaks are larger after irradiation than before.

* Over-biasing improves charge collection 1V/µm versus 3V/µm

* More systematic and

quantitative studies are underway.

## Conclusions and perspectives

DIAMMONI beam monitors are designed to satisfy two modes of particle counting and would permit to cover a wide range of beam intensities.

Simulation studies are underway to optimize detector geometry.

Electronic developments are in progress at laboratory for the detector readout.

Experiments in ARRONAX cyclotron with 68 MeV protons conclude to a linear diamond response with beam intensity, but it also reveals damaging issues. Studies on this point are underway.