The panel may appoint persons it determines to be disinterested and qualified experts to make any necessary professional or expert mental or physical examination of the plaintiff or review of the relevant evidentiary matters, and testify or submit a report in respect thereto. The panel shall give notice, reasonable under the circumstances to all parties, of its intent to appoint such experts, and shall allow them a reasonable time within which to communicate to the panel any objections they may have to the appointment of such experts. Such expert witnesses shall be allowed reasonable and necessary expenses connected with their travel, meals and lodging in connection with their testimony and work on behalf of the panel as well as a reasonable fee to be fixed by the panel and paid pursuant to § 6813 [terminated] of this title.